Regression to the mean

Measure anything that varies and the extremes will mostly be luck stacked on top of skill. Luck does not repeat, so the next measurement drifts back towards your normal. A video that triples your average is followed by one nearer the average. Nothing caused the move. This is where a great deal of creator superstition comes from: you change something after a bad run, the numbers recover on their own, and the change takes the credit. The defence is a rolling average across several uploads.