Of course, maybe in the future there will be a new coin that will be protected from such manipulations, but it will take at least 5 years to restore trust for people, I think so
Well, before we talk about restoring trust, we should discuss whether it's possible to lose it in the first place. If there is a chance that an attack will happen, I'm pretty sure the community will prepare for the countermeasures. Your panic sell situation has been described and predicted multiple times but Bitcoin is still doing fine. Sure, everyone knows 51% is deadly, but it's not like anyone can pull the trigger and kill the network anytime.