The "left" didn't lose. Clinton lost. The centrists and right-wingers (remember, for us in the UK and NZ, both US political parties are right-wing) have to take a good hard look at themselves. But, like you, they seem to prefer blaming leftists.
You don't understand my point anyway, so hey
To be honest, it really doesn't sound like you're interested in the thread here. It's reading like you came here specifically to pick holes in a tangent you haven't actually read fully. I could be wrong, sorry, but I'm putting this out there upfront so it doesn't sit in my head niggling at me (and colouring any possible response).
The voters aren't mind-controlled, no. However, a potential candidate has two hurdles. One is some level of popular support. The other is support of the establishment. I'm talking about the latter problem at the moment.
As an aside, the Republican establishment pivoted to backing Trump (or started to in significant numbers)
as soon as the wind starting turning in his favour (that article is from May 2016, well before the actual election of that year, and ahead of the important party conferences in the summer).