The swing was predicted in advance in British media. Trump encouraged his supporters to vote on the day, partly in an attempt to dampen down fears about Covid. Democrats in general were more concerned about Covid and were encouraged to vote in advance/by post. Hence they predicted a "Red mirage" on election day and then a "Blue wave". That's why there has been such a shift.I haven't read all of the comments, but my take on the US election is as follows.
Trump really is a classless piece of shit and in my opinion deranged. Saying that, both candidates are very poor for different reasons and, if that's the best the US have got to offer, they have big problems.
Also, whilst I don't believe Trump's claim (and, if there is any truth in what he says, let's see evidence), the voting and results do seem very fishy. Overnight there were a raft of results counted - including some big States - and it was fairly even with Trump fairly well ahead in most of the outstanding States. It has then taken at least two further days to count the remaining votes with Trumps lead in several States ebbing away. From the outside, looking in, it looks very fishy, but, as I say, Trump will need to provide evidence to prove it's a fraud rather than just a bit fishy looking.
Agree re poor candidates (ours not much better tbh). However, Trump is uniquely shocking in that he is questioning the veracity of the whole system (on no credible evidence). Even Nixon gave a generous speech conceding to Kennedy in 1960 and said he would support the incoming President. Worrying that Trump may have blood on his hands if some of his extremist fans to resort to violence as a result of his irresponsible language and claims. Dangerous and classless.
Hope my language in describing Trump wasn't too offensive Shotshy. :-)