You know, when Hillary lost, she didn't spend the next month or so hollering about voter fraud like Trump has.
And, while many people didn't like the fact she lost, most accepted it and moved on, even though they despised Trump.
As far as why did Trump win in 2016, and lose in 2020? Well, in 2016, we didn't know much about him or how he would lead. In 2020 we had concrete evidence of how crappy a leader he is, and that is why he lost. I've seen and talked to many people about how they voted for him in 2016 when they thought he would be a great leader, but then voted against him this election because they had 3 1/2 years of his incompetent leadership that he constantly demonstrated.