Why did the cupbearer forget Joseph after he interpreted his dream and the bread makers?

Genesis 40:18 “This is what it means,” Joseph said. “The three baskets are three days. 19 Within three days Pharaoh will lift off your head and impale your body on a pole. And the birds will eat away your flesh.”

20 Now the third day was Pharaoh’s birthday, and he gave a feast for all his officials. He lifted up the heads of the chief cupbearer and the chief baker in the presence of his officials: 21 He restored the chief cupbearer to his position, so that he once again put the cup into Pharaoh’s hand— 22 but he impaled the chief baker, just as Joseph had said to them in his interpretation.

23 The chief cupbearer, however, did not remember Joseph; he forgot him.

Why did the cupbearer forget him? Did he really forget or was it something else like pride or fear? Did God make him forget Joseph?

I believe that the answer to your questions is found here:

Psalm 105:17-22

"He sent a man before them, even Joseph, who was sold for a servant: Whose feet they hurt with fetters: he was laid in iron: Until the time that his word came: the word of the LORD tried him. The king sent and loosed him; even the ruler of the people, and let him go free. He made him lord of his house, and ruler of all his substance: To bind his princes at his pleasure; and teach his senators wisdom."

The fulfillment of the dream which God had given Joseph in relation to him ruling over his brethren did not come until the time of God's perfect timing. With his call to power came the need for the character to fulfill such a calling, and while Joseph was going through his ordeals, the word of the LORD was trying or testing him.

I think that we see this same principle in the life of Moses, who spent 40 years tending to his father-in-law's flocks before fulfilling his destiny of being "a prince and a judge" (Exodus 2:14) over God's people, and in the life of David, who spent years hiding in caves and the like while running from King Saul before fulfilling his destiny of being a king over God's people himself.

Quite frankly, I hope that this same principle is at work in my own life. In other words, I do not believe that I have come close to fulfilling that for which I was created yet, but I am ever allowing God to form his character in me as I grow in my own walk with Christ.

Anyhow, I hope that this at least partially answers your questions.

Divine providence...Joseph would not be ready to rule Egypt (by God's reckoning) for another two years.

Psalm 105 v19: "Until the time that his word came to pass, The word of the Lord tested him."

This is actually what is going on in most Christian's lives. Our failure to recognize this is what often leads to our dissatisfaction on a daily basis. Philippians 2:12-13 instructs us to work out our salvation in consideration of the reality that God is willing and doing of His good pleasure in us.
We should see everyday as a new adventure. We should get up with a hopeful expectation each day that the God of all glory is so intimately involved in our lives that He has planned an awesome day for us.

That's because he is so smart.

Fine. That's because he's so heart.

It says the chief cupbearer did not remember Joseph but forgot him, so it sounds as if he did not know Joseph.

But after 2 years had passed Pharaoh had a dream and then it came to the chief butler's mind about Joseph and how he had interpreted his dream and could interpret Pharaoh's dream.

This seems like it could of came from God to withhold the information from Pharaoh for it was not Joseph's time to be loosed from prison until 2 more years which then he would interpret Pharaoh's dream causing his rise to be second in command of Egypt, and then help his people who came there which they found favor with Pharaoh until a new Pharaoh rose up that did not know Joseph and they eventually lost favor.

Which was part of God's plan to deliver the Hebrews and show Egypt and the surrounding cities of his power that He is the one true God.

Perhaps the lesson was to ask God not to forget us rather than asking someone else.

It has to do with God's timing for Joseph --the cupbearer was not suppose to free Joseph -----Pharaoh freed him when the cupbearer though about Joseph when Pharaoh had a second dream and wanted to know what it meant ------then the cupbearer remembered Joseph was in prison and could interpret the dream for Pharaoh -----and brought him to Pharaoh -----then Pharaoh freed Joseph from Prison ------

God never left Joseph -----God was using Joseph for His purpose -----and there is a right time that only God knows for the good to happen in a bad situation -----and this is where our patience come in as God will give us the ability to endure the bad situation until the right time has come to be released from that bad situation -----so the good can come to pass ------

Joseph was trying to get his own way by using God's special gift that God gave to Joseph for His purpose--he was using his gift with the wrong motive ----to get freed ---and God stopped the process by putting Joseph out of the cupbearers mind -----

So great lesson here for us to know when we who are God's true Children get into bad situations and by our own methods can't get out of the bad situation ---to remain steadfast in our Faith and trust that God will get us out at His timing ----so we experience the good that can come out of the bad -----

Because it required for Pharaoh to be Troubled by Dreams.
Had the Cupbearer said to Pharaoh, I know a man who interprets Dreams, it would mean nothing to Pharaoh.
But when Pharaoh became "troubled by his Dreams," he was now in position to be told about Joseph.

Clearly, Joseph, was ready to Rule because he had God.
But the Pharaoh was in NO PLACE he wanted a Second in Command/Helper yet.

Because of the number 2.

Sounds ridiculous?

Well this story and the story of Esther have a LOT in common with the establishment of the symbolism behind the number 2. (At least as God intends)

Two is the number that the Jewish system of counting and numbering begins. The first of anything belongs to God and it is NEVER counted, measured, said, or stated.
But basically it is the number that symbolizes Jesus's relationship to the Father. How Jesus advises his Father(THE KING OF KINGS) about what to do.

This is the core of the focus of these stories.

And I'm not suggesting that we worship a pantheon or something idiotic like that. Just that this is what was revealed to the Jews about the Messiah to come.

The deliberately slow revelation of Jesus across the whole of the Old Testament is a rather unique revelation....everything about Jesus was already pre-figured across the entire Old Testament including his appearance, career before His ministry, and every action and location before He finally arrived.

And it's interesting that the cupbearer says 2 years later! "Today I am reminded of my shortcomings." Like the employee who gets promoted and has it go to his head.

So to me the cupbearer was intimidated by Joseph and chose to keep quiet. I'm not sure if it was God's will or not since it was envy that caused it. But that God gave the cupbearer a 2nd chance (this time possibly being put to death if not helping the Pharaoh) to be honest. So to me God was saying "okay you don't want to do the right thing by Joseph, then I will force you into it by giving the Pharaoh a dream that needs interpreted or death will come to you."