The very Trumpy decision

Once Trump indicated 10 days ago that he would not sign a second waiver, national security adviser H.R. McMaster began putting together options that officials assessed would result in the least damage.

[...]

The debate came to a head at a White House meeting Nov. 27 to hash out the waiver issue. According to people briefed on the meeting, Trump repeated his earlier assertions that he had to follow through on his campaign pledge, seemingly irritated by objections over security and the break with previous policy.

[...]

According to Nabil Shaath, an adviser to Palestinian Authority President Mahmoud Abbas, Trump “just went on saying he had to do it,” despite the Palestinian leader’s fervent objections.

[...]

While Trump appeared to have made up his mind [about Jerusalem], he continued to solicit input, two White House officials said, even asking random acquaintances about the Middle East in recent months.

  WaPo

So, he was soliciting input from random acquaintances when his cabinet officials were squealing he shouldn't be doing this? In other words, he was soliciting approval, not measured input.

Several advisers said he did not seem to have a full understanding of the issue and instead appeared to be focused on “seeming pro-Israel,” in the words of one, and “making a deal,” in the words of another.

I think that last one hit the nail on the head. He promised his base, and now he's delivered. Win!