Most active manager performance is mean reverting. They have a good year, and then there is little evidence of persistence in their future returns. Here's a larger study from S&P:

https://www.spglobal.com/spdji/en/documents/research/researc...

"We observe little to no evidence of performance persistence among active managers, except in the large-cap value and real estate categories. For example, out of 1,034 large-cap funds that existed in the universe as of Sept. 30, 2013, only 19.73%, or 204 funds, outperformed the S&P 500. In the following year, 15.69% of those 204 funds outperformed the benchmark. By the end of the third year, none of those original 204 funds were able to outperform the S&P 500 on a consecutive basis."

What is implied from this data is that if a manager has a good year, they are unlikely to match it going forward. So only 20% beat an index, and then only 16% of those that did beat it the next year.