How do you know any strategy is attributable to success or failure without testing it?

Pre/post analysis may be temporally correlated but this isn't proof because you haven't captured a baseline comparison.

A/B and MAB testing are helpful but not magic bullets.

Shapley values (marginal impact) is a nice mathematical outcome to have for multitouch attribution but as usually implemented is only a single statistic and can be a fluke without additional testing.