There's a great reminder in this article from FiveThirtyEight for all the Democrats out there that are wondering why some of President Trump's opponents in his own party aren't doing more to stop him:
Just because they don't like their own president doesn't mean Senators Flake or Collins or any of the others have stopped being Republicans. They're not going to stand in the way of tax cuts, or repealing the ACA, or confirming conservative originalist judges, just because the person leading the charge is someone they don't personally like; these are all things they've wanted for longer than President Trump has been the Republicans' standard-bearer.
That doesn't mean their support is harmless - the end of the article points out that handing the president policy wins helps to bring the rest of the GOP together behind him - but it is still quite understandable. They may not be limiting the president as much as Democrats might want, but I'll take what we can get - and if the Democrats want more than that, well, they'll just have to win as much as they can in the midterms.