Both the points you mentioned apply. To expand further - sectors / classes tend to behave cyclically (if there was a consistent winner everyone would always buy in), so past winners tend to start losing due to regression to the mean (a question of when not if).

Also, one could argue that ARK success is just a bubble fueled by a mob of unsophisticated retail investors. I've seen many comments saying that ARK is invincible forever and that there's no point in buying anything else, or that their 5-6 years if success makes more than 100 years of conventional investing wisdom worthless.

There's also general investor behavior - studies consistently find that FOMO driven trades lead to poor returns.