I'm going to poke around, see what I can figure out (I know there's the goggles thing I can do on mempool.space) but if anyone knows offhand, it would be great to know!
This is not the first time, the last time it happened it occurred was on the halving day. The Runes protocol has been clogging blocks since then. It can be because of that (not too probable tho). This can also be caused due to Inscriptions (Ordinals / Runes / BRC-20-like spam). These are like NFTs on Bitcoin that jam the mempool with large, complex transactions.