That makes no sense. Egypt won’t let them in because they can’t go back?
Yeah. It's that simple. If you do some research it won't seem like stochastic calculus.
Even people who seek asylum can be sent back if their claims are denied. Israel does not allow Palestinians in the diaspora to return to Palestine.
And the countries surrounding Palestine don't want the burdens that come with absorbing millions of destitute refugees.
But most importantly, the surrounding countries know that once they provide the option for Palestinians to enter and reside in their country, Israel will conduct a final solution to push all Palestinians to said country, kill whoever refuses to go, and take over Gaza and the West Bank.