Senator Warren's Endorsement of Clinton: Sanders' Progressives Betrayed?

I think it is very naive and misguided for those with a strong preference for Senator Bernie Sanders (I-VT) over Secretary Hillary Clinton for the Democratic presidential nomination to view Senator Elizabeth Warren's (D-MA) endorsement of Secretary Clinton as a betrayal and to therefore abandon all support for and good will towards her.

The endorsement, occurring when it did on June 9th, is clearly perfunctory at best.  It came after the June 7th date that was primary day in California, Montana, New Jersey, North Dakota, New Mexico, and South Dakota, states who together had at stake a total number of pledged delegates great enough to have allowed Sanders to potentially overtake Clinton on that score--great enough even to have potentially allowed him to clinch the nomination outright and on pledged delegates alone.  The endorsement came not only after it became impossible for Sanders to overtake Clinton in the delegate count, but it came after every state's primary, and after every primary save for one--a smaller, lower-stakes one: D.C.'s.  

For Senator Warren to have held out as long as she did from endorsing Secretary Clinton, including through breaking with Senate allies to be the only exception to the en masse endorsement by the rest of the Senate Democratic women, militates against the idea that her ultimate support is a betrayal of Sanders and his progressive supporters.  For her to have waited any longer, until after every primary had taken place or after Sanders himself had conceded or Clinton had been officially nominated at the convention, would have negated any remaining value in her endorsement at all and been entirely pointless: it would not have earned her any good will from the potential next president or her co-legislators.

So Senator Warren's endorsement of Secretary Clinton came after the ultimate outcome of the party's presidential primary was virtually already determined--assuming only that, plausibly, the bulk of the unpledged "superdelegates" will remain for the 'establishment candidate' over the 'insurgent' one.  Thus, Warren's endorsement of Clinton is better described as being for the general election rather than for the primary; looked at in this way, Warren did not endorse Clinton over Sanders at all, but only over Republican presumptive nominee Donald Trump.

Sure, one could argue that it's not Warren's endorsement of Clinton that is the betrayal; rather that it's her non-endorsement of Sanders that is.  Maybe so, but if that is the case, then the reactions to her endorsement, coming when and as it did, that see it as a betrayal are groundless and the accompanying condemnation of Warren as a traitor is late, not occasioned by any occurrence, and is simply a restatement of a preexisting view and not a new conclusion drawn from new information.  One cannot maintain both that that her failure to endorse him was not a betrayal but her endorsement of Clinton was.