You don’t even understand the simple fact that the reason these in this second group were being persecuted is because they were in fact believers.
- he who hears the word and immediately receives it with joy;
20 But he who received the seed on stony places, this is he who hears the word and immediately receives it with joy; 21 yet he has no root in himself, but endures only for a while. For when tribulation or persecution arises because of the word, immediately he stumbles.
These in this group did believe, and received it with the joy of salvation, and went around witnessing and were eventually persecuted by unbelieving Jews in an attempt to cause them to return to Judaism.
The fell away, which means they stumbled and turned away from Christ.
They returned to unbelief.