Worse, if the overall Ethereum community reaches a consensus that a malicious entity attempted to take over the network, then the devs will fork the blockchain to rollback the particular transactions with the malicious entity, and the new blockchain will keep chugging along as normal while the attacker has just lost a shitton of dollars to buy 100BB. (This is similar to what happened with the DAO previously, although the reason for it was bugs rather than a 51% attack)

This is not what happened with the DAO. This is well documented and I suggest you read up on. TLDR, the hacker tried to withdraw the funds and there was a 30 day lockup period so the contract was updated to stop this.

My understanding was that an illicit fund withdrawing was possible because of a bug in the contract code (more specifically a recursive call loophole), and the community executed a hard fork to return those funds to their original owners. I’m curious as to what I’m misunderstanding here.

There have been multiple examples of 51% attacks happening and the cryptocurrency it happened to not going to zero.

Etherum classic and Bitcoin gold come to mind. They are both in the top 100 still, and both have been 51% attack multiple times.