The socialist-democrats need to rally their illegal alien voter base for this fall. By deliberately dropping the ball on the whole DACA thing, they can put all of the blame on President Trump and the republicans.
Only because the MSM will beat that drum until elections time. Trump offered, and they refused.
He needs to veto this and stress that he is doing so because the Dems have abandoned DACA and refuse to build the wall to protect American citizens.