PoW vs PoS in the event of a 51% attack

First off, people say that 51% attacks are irrelevant because the attackers would lose money because it would devalue the coins they are holding or devalue their mining equipment, but what if these people are heavily shorting the same crypto they are attacking. They would have to sink a ton of cash into shorts but they could be leveraged to the tits because they knew it would be a sure thing. If the attackers are a group of very rich people or a corrupt government then it seems plausible to me depending on the size of the given crypto network.

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If this said group owned 51% of all ethereum or any other proof of stake crypto, would forking off be a viable option? I don't think it would be because those stakers could just move their stake over to the new forked off chain and maintain their 51% majority. How could the protocol be changed in order to unseat these bad actors?

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However, in the case that a proof of work crypto was attacked. Then couldn't the users fork off with a new protocol that makes the bad actor's mining equipment obsolete. Similar to how monero's protocol changed in order to make asics unprofitable for mining.