If the members of the church knew about it and did nothing, then they’d have a measure of culpability, too.
I agree and if the hypothetical church members knew about it but did nothing, they have much more than “a measure”: of culpability. They would have civil liability, and possible criminal liability as well/
However, there is no evidence nor proof Sasse ever knew about it. By the way, the standard of proof here is about 98% percent, far from “a guy told a guy who told a guy” that one often sees in these accusations.