I'm with you. I'm not buying it.
Pres. Trump was manipulated into this mess by the legislative leaders in his own party. On top of that at the last moment Trump could have said "NO!" but he didn't. Conservatives were sold out by the Pub party again and Pres. Trump went along with it.
At this point, I think the best we can hope for is Pres. Trump to be strong on foreign policy and trade. The Rats will win back the House in 2018 and probably the Senate in 2020, not a rosy picture. When George Bush (41) raised taxes after promising not to the Pub establishment deluded themselves into believing it wouldn't hurt them. The same holds true for Trump and the Pubs not repealing obamacare, not building the wall, and not reforming immigration.
I have never been a Trumper, but I think you have overlooked why he signed such a lousy bill. It was largely to get funding for the wall, which you can bet he
will now start building. You seem to be presupposing that he won't do it, even though we have plenty of signals that he will give a big chunk of the military money to the Corps of Engineers.
Another likely reason why he might have felt it necessary to sign the bill is that he cannot afford a shutdown right now--not for political reasons, but for reasons of military preparedness and possibly military justice (including but not limited to imminent actions against sanctuary cities).
Anyway, Trump claims to have a strategy for wiping out the national debt. Let's see what he does.