I'm not certain he "caved". In fact, my opinion is that this was a tactical move.
This is how I see it:
It started with drawing the proverbial 'line in the sand' - Build the wall.
He baited them by saying he would own the shutdown.
This gave them an air of confidence to hold their position and allow the shutdown to happen.
I don't think they expected it to last as long as it did however.
Throughout the shutdown, at the risk of losing his base, he continually shifted his position culminating in him completely backing down and giving in to the democrats.
This made it appear that they won.
What really happened though?
He forced Nancy and Chuck to go full retard.
He made them choose between not only American citizens but DACA recipients too.
When they chose to stand their ground, they chose politics over people.
You may not see it but the are now millions of people who once stood with Nancy and Chuck are now questioning their loyalties.
The real question is; WHY?
I think it's a set up.
He gave them exactly what they wanted.
What happens over the next 3 weeks?
The SOTU should take place Tuesday but Nancy already said that likely won't happen.
What happens if Nancy and Chuck continue to refuse border wall funding?
Eventually, 3 weeks will pass and we will be facing another shutdown.
Who will be af fault this time?
Can Trump negotiate down any further?
We watched Trump give and give to the point he gave them exactly what they want. Now we are about to witness 3 weeks of more one sided negotiations. At the end of 3 weeks, if need be, he will declare a national emergency and let the Mil build the wall. It will immediately be challenged in the courts but he's already set the stage and the courts will quickly studder with Trump.
That brings me to part 2. I think something else happened as well. My guess is RBG will retire/ pass away over the next 3 wks. thus opening up another SCOTUS pick. Conservatives will have complete control of the SC and he will win the decision 7 - 2.
Obviously, this is all speculation but it stands to reason that something is going on behind the scenes the public isn't privy to. These behind the scene moves are where the magic happens. Guess we shall see Tuesday.
Trump isn't that savvy to craft a plan like that. He blinked, at that's pretty much the end of it. For all the negative press he's getting from even right-wing media, it's obvious he's seen as having caved to Pelosi.