What is a strong proof of widespread voter fraud? A confluence of high improbabilities, all favoring a single candidate. If you had a handful of improbable events, (roughly) evenly distributed between presidential candidates Trump and Biden, you could dismiss these events as happening according to chance: however, a pile of high improbability events, all favoring a particular candidate, shows with very little doubt, voter fraud has taken place, in a deliberate, coordinated way.