How do you count almost 40 million handwritten paper ballots in a matter of hours and declare a winner?

Well, that regularly happens in UK elections. You just need to have lots of people doing the counting in lots of places all over the country. In itself the speed of the count isn't a knockdown argument for cheating.

Which isn't to say it may not have been a fix - none of us (including the people writing comments columns in the media and online) have enough information to make it possible to reach any firm conclusion.