Remember when he was winning and then there was a "software failure"
This sounds like a dangerous Qanon conspiracy theory to me. All the sources have told me that electronic voting machines are 100% secure. So that must be true and you must be wrong.
/s
The obvious triangulation against him by the party probably didn't help. I don't care about Sanders any more than I care about any candidate suggesting we step back from the brink, but it was so obvious even people who spend all day on Twitter calling everyone "Bernie Bros" (even people who aren't bros) got a little suspicious.
Same as happened to Ron Paul in some way. Candidate seek to change the course of a party and is stop by existing party interest.