Trump likely caved because McConnell told him there are enough votes to override a veto. Republicans don't want to go through shutting down the government again.

They offered exactly what the previous year's border security funding was, plus some minor tweaks.

Ironicaly, that's almost exactly the same thing that passed the Senate by unanimous voice vote in December AND it's less than any of the several compromise offers made during the shutdown. Which makes the entire shutdown stunt and its orange-hued proponent look even more pig-headed.