A lot of it isn't organised. It's just their innate psychology. They'll think well if we let more votes in after deadline it's more democratic right, making everyone's vote count. They also genuinely believe that it's a good thing to get Trump out the same as you might automatically think it a good thing to help an elderly person up that has fallen over.

You're assuming that there even needs to be a reason for it to be obvious. It's not entirely coordinated. People have already been programmed to do it without thinking they're doing anything wrong. In fact it's the reverse. Given the chance they feel hey're doing something wrong if they don't cheat.

That's not to say their aren't coordinated efforts as well but it's more complex than some kind of mega centralised scheme.

If you believed Trump was Hitler and the situation you were in was dire like being under Nazi occupation in WWII and were sitting there counting ballots what would you do? They think they're like the Jews sabotaging bombs when forced to work in the factories for real. It's so easy to miss a tiny part out or to miss a part. That's their mindset.

The democrats trains their minions like that (supporters) and it really means they're basically unemployable in anything requiring integrity, responsibility and trust. If you're an employer you should discriminate against people based on this criteria. Some will be innocent but given the enormous proportion you just can't risk it.