I've heard this sort of explanation before. What is your source?
The streets of Jerusalem were very narrow. When Jesus was taken before Pilate at dawn, the crowds had gathered outside the justice hall. Where had they come from? How did they know about the secret trial of Jesus? The answer is that they didn't. The Galileans were waking up and preparing for festivities with no idea what had happened. Why would they stream into the narrow streets of Jerusalem at dawn and make their way to Pilate's residence when they were preparing for the first day of Unleavened Bread. Besides there would only be room for a hundred or so at most before Pilate's residence. Those who had gathered would be those who hoped to take advantage of the offer of the release of prisoner. Two zealots were being put to death that day. Their leader Barabbas was clearly due to be tried. On this special day when they could ask for a prisoner to be released to them, who would gather? Certainly a good number would be zealot supporters who wanted Barabbas released (it is clear from Pilate's words that he expected such to be there). . Others would be vindictive Scribes and Pharisees and their supporters who did know Jesus was to be tried. There would also be disinterested spectators who lived nearby in Jerusalem, and liked a spectacle. There was hardly room for anyone else. Certainly not a hundred thousand Galileans.