Your overlying point is correct. Chubb is one of the most naturally talented RBs in the NFL, but it's contradictory to note that he spilt carries (with Kareem Hunt), and then also call him a bell-cow. There are very few offenses in the NFL that implement a single back (bell-cow) system, anymore. Cleveland has two guys that could probably start for over half the NFL in Chubb and Hunt. They are smart to deploy them in a running back by committee approach to keep them fresh and healthy.
The real evidence on Chubb is that he was 7th in total rushing while also missing 4 games due to injury and splitting carries with Hunt. He was 2nd in the NFL in total rushing the year before, in 2019, while playing all 16 games.
You could also have noted Todd Gurley, who was once considered a top-3 RB in the NFL until his knee rotted away over the past two seasons at a very young age. Currently a free agent at age 27, he is having a hard time sniffing a contract because of that knee, but in 3 of his first 4 seasons, he put up...
=1106 yds/10 TDs as a rookie in 2015
=1305 yds/13 TDs in 2017
=1251 yds/17 TDs in 2018
Across his 6 year career, he has 8336 yds from scrimmage and 79 TDs.
D'Andre Swift is another worth mentioning, though still in his infancy as a pro. He was a 2nd rd pick, last year, and split carries as a rookie with the Lions but is considered one of the more promising young backs in the NFL and should receive the majority of work in Detroit, this season.
Sony Michel has been a bit of a bust in the NFL, so far, in New England.