Understanding how Trump works and "dumbest thing ever" are not mutually exclusive.
Advocating for a plan to move an entire population out of lands that they have occupied for almost a century now is "ethnic cleansing." It is not necessary to tie that to a genocide. The forced expulsion is enough. And make no mistake, there is a large part of that group which will not move voluntarily. And of those that do move, there will be a significant number calling for a "return to the homeland" by any means.
I don't disagree that sometimes "shaking the box" is a viable course of action which can lead to a favourable result. I just do not see it in this case. What positive outcome do you (as Trump's alter ego who seems to perceive a plan) see from this suggestion that will lead to a permanent solution to the "Palestinian problem," considering that the vast majority of the world sees this as the "Israeli problem" in the first place?