Since all these forks are based of yuzu souce code and the developers admitted it was primarily for piracy, doesn't this make these all an easy target to take down? I think this might prevent a true successor with active development from emerging.
No. Their statement as part of a settlement has no bearing on unrelated parties. It's not precedent.
And the code is already open source, so anyone and everyone has full rights to do anything they want within the license. No one is capable of DMCAing it (or rather, anyone is, but the author can trivially point to the license giving them the full right to modify and redistribute in a counterclaim).
I don't get why people are down-voting you. It's a perfectly legit question that I'm thinking about myself. I'm not a lawyer but there would be ways to shield yourself legally I'm sure.