Maybe they're trying to cover their bases? I don't know what contracts they had with BWF for appearing on the channel during their whole streaming journey, but I imagine they didn't have ironclad contracts when they were under Geek & Sundry, and only got the particulars down more concretely when they established their own company/channel. Those terms may have also changed once BWF was let go.

From how I understood it, BWF was also trying to blackmail Ashley for money, and the fact that he still appeared on the channel while no longer being paid may have contributed to that sentiment. So by having BWF-centric content wiped out officially, it cripples any murky legalities he can claim.

I'm not sure it makes sense to make a call on whether this is the right/wrong decision when we know next to nothing about the specific reasons leading to the removal.

Could be legal reasons, could be something in BWF's contract, or maybe it's purely for the personal comfort for Ashley (which if so, overrides anything else imo). We do not know.

I'm sad to lose the content too. Especially all the insight from the cast, and the BTS interviews. But I also cannot blame them for removing it, it's totally within their rights to do so.

yogscast is another example. Some creeps in the network got exposed, they put out a public statement but they did not remove any previous content with those people in it.