I could think of at least four possible reasons to doubt their accusations. Some of which wouldn't sit well with people.

1. The accusers are being blackmailed into doing it. 2. Or they are being bribed by people wanting to influence the election. 3. Or they want to be famous. 4. Or they have a personal vendetta against Donald Trump.

There is a reason we have courts, trials and burdens of proof. And the convenient timing of some of these accusations doesn't help, either.