I’m glad you think that obvious, as you are completely wrong. But let’s delve back into your fantasy... Who is going to put their signature down on the falsified FEC filing and risk going to jail to hide the origin of the bots posing as donors? They can’t put it down as a bulk donation; they have to match the records of contributions to the contributor.
Again, if it is just a big check from Soros, just give it to a PAC or other non-hard money campaign cash dump.
The website in question are contributions directly to the campaign, the most restrictive (and record intensive) form of political contribution.
Occam’s razor: The simplest explanation is usually the correct one.
A script to change the numbers every minute or so to inflate contributions (there’s no federal requirement preventing campaigns from lying about how much fictional money they receive) is the most likely explanation for the steady increase in donations reported on the website, even in the middle of the night.