// I don’t think that's what cost Theresa May. I think her stance on Brexit that did that.//
At the times, she was saying "Brexit means Brexit", had called the election on the grounds that Parliament was blocking her efforts to deliver Brexit, and shortly after she'd signed legislation triggering Article 50. From 2017-19, I'm sure you can legitimately make a case that her stance on Brexit wasn't enough to appease Leave voters, but in 2017 it seems odd in the extreme to say that her "stance on Brexit" cost her the Election -- unless you mean that Remain voters didn't back her?
Because, as I say, we only had a 2017 Election in the first place because, in her view, she needed a bigger mandate to deliver Brexit.