It’s both more and less than that.
A lot of Socialists ended up turning into Fascists in the 20s and 30s (See: Moseley, Mussolini) not because of any affinity between ideologies (as certain people on the right would claim), but because talking up economic redress to desperate, starving people is a great way to get a support base which is personally loyal to you, regardless of what ideology they preach. When those would-be-Socialist demagogues learned that if they flipped right, they’d be subject to a lot less uh… peer-review from the Gramscis and Atlees of the world, they had no trouble profiting.
The problem is that to people who have historically found themselves on the business end of that sort of dynamic, it’s going to take a lot for any kind of populist to prove that they’re actually in it to make peoples’ lives better, and not to build their own personally-loyal power base.
And IMO, Sanders hasn’t been doing a very good job of that.
Americans describing Trudeau as some kind of hyper-stalinist whilst sharing the same FB wall as my more local friends complaining about how he’s been offering up more empty platitudes than action (which is a valid complaint, IMO) is always good for a chuckle.