Yglesias:

Republican leaders -- both Mitch McConnell and Paul Ryan, as well as Ryan's predecessor John Boehner, and the chairs of all the relevant committees -- spent years and years lying to everyone in sight about Republican health plans...

Trump, of course, very much falls into that core audience for Republican Party spin. So when Republican leaders said over and over and over again that they had a plan to replace Obamacare with something better, Trump naturally developed the opinion that they had a plan to replace Obamacare with something better. And if they had had such a plan, it wouldn't have been difficult to pass it...

...All that said, Trump is president now. On the campaign trail, he outlined some humane and politically popular ideas about health care policy like that Medicaid shouldn't be cut and that the United States should have a system that covers everybody even if that means the government needs to pay for it.