Obama didn't kowtow to calls to be more moderate, he worked to get done what was possible. He went into health care reform wanting a proper public option, but it became obvious that the "blue dog" Democrats wouldn't vote for something that progressive. It was get what ended up the ACA done or nothing at all, and even getting the ACA through was a massive slog and almost didn't happen.
And soon after, Republicans took the House. This is what I mean about people not recognizing that we don't elect emperors--you can't just get anything you want done as long as you care enough or believe enough. There was no way in hell a Republican House was ever going to vote through more progressive legislation, so Obama tried to get more moderate things done--things that incrementally moved the needle rather than holding out for things that had no hope because the opposing party obviously had no reason or incentive to go along.
You're setting Sanders up to fail you even if he did get elected President. You seem to think he can get his agenda through via sheer force of will. He can't--he needs a majority of the House and Senate to agree with him. If Republicans control either chamber (and, right now, odds are Republicans will still hold the Senate), his agenda is dead on arrival. And even if Democrats win the Senate, it'll be by a tiny margin. Any defections will tank more liberal agenda items, as Obama discovered. Then it'll look like Sanders either was ineffective or else kowtowed.