Isn't the push behind Biden "making the best of a bad system"? Which seems to be exactly the same sentiment behind "I don't like the oligarchs but it's useful that they agree with me."
Not sure what article you're reading, but this one didn't seem to imply the reason for ceasing donations was being against oligarchy. So I'm not sure what point you're making?
You think Biden is a legitimately good candidate and not just worth rallying behind to stop Trump?