In 2024, there were 35 RBs out of 134 schools who ran for 1,000+ yards. That's 26%.
So if you had a 26% chance of having a RB on your team with 1,000+ yards, in 9 years, 2.35 of them would be expected to have a 1,000+ yard rusher.
Using the binomial distribution, 81.3% of teams would have no more than three 1,000+ yard rushers in 9 years.
Is it some massive failure that BYU has only had three 1,000+ yard rushers in the last 9 years, especially given a heavy dose of injuries in several of those seasons? Not particularly.