Whatever be the motive, Trump has voiced his displeasure on this
It's really quite simple, he saw the opposition to it from the public, he saw how unpopular it was and worked out it probably wasn't the best way to start off the New Year.
@Raoul has said he could be malleable a few times and I think he could be right, be it from blackmail from someone like Putin or his criminal friends (he was seen partying with a known gangster on New Years Eve) or be it from swaying him due to public opinion.
It was obvious to many that he was only ever in this for himself and he really is going to upset everyone at some point or another. He's already laughed and mocked his own supporters at his acceptance rallies directly to their faces, now he's pissed off a few Republicans and gone against what KellyAnne Conway said AGAIN! as he did that a week or so ago too. She won't put up with that too many more times, she can't, and Republicans won't take being pissed around all the time either. It's also clear (if it was ever in doubt) that he has no loyalty whatsoever, and he doesn't care if his supporters are Republican, Democrats, Communist or even KKK members, as long as they support him, like him, and praise him. He won't care much at all where the support comes from, just as long as it is support and some of his policies could easily be influenced just because of that. That's not bad news really, especially when you consider that for most of his life he's been pretty Liberal on lots of issues, despite being a complete moron and spouting loads of right wing nonsense just to get votes before the election.
After stuff like this today I feel a bit better about it all as I can see his impeachment more likely than not, and also him actually putting through some actual decent changes because of how popular it will make him with the majority of the public, or him not following through on many of his campaign promises just because of how unpopular it would make him, his need for adulation from the people could see him backtrack and flip flop on many issues. We have already seen it with this, with locking Hillary up, the wall, mass deportations and much more.
Although maybe that could just be wishful thinking on my part.