I didn't say she actively wants the party to lose, just that maintaining her access to fundraising that keeps her relevant as a force internally in the party is higher priority than the party winning.
As to the Democratic field, most of them are using Medicare for All as a slogan and intentionally not defining the policy that they actually mean when they say that. Which is why they use the sleazy qualifier "some version of" Medicare for All. What they mean by that is "Something other than Medicare for All". The Jayapal Bill is the standard since she introduced it this session, but I wouldn't nitpick if someone said the Sanders bill is what they mean when they say M4A.*
Sanders obviously supports M4A. Warren has hedged in the past but unequivocally expressed support for it at the debate and hasn't said anything contradictory to that since as far as I know. Harris also indicated that she's in favor of a single payer plan at the debate but she backpedaled and claimed she misunderstood the question within 24 hours.
So Sanders supports it and Warren now supports it too, which is a recent development if you've actually been listening to her. I guess de Blasio also does but who cares.
* I do not count Senators who cosponsored Sanders' M4A Bill as supporters of the policy in their capacity as a candidate for POTUS unless they have explicitly stated they support it while speaking as a declared candidate.