and there's the temptation to govern in a permanent crisis mode. there is no end to reasons why there is a crisis. or, is there a scientific definition of "crisis"?

Yes, I agree that there is a temptation for those in power. Legal frameworks can be created to try and limit the lengths and conditions under which a "crisis mode" can be enacted, but there will always be people looking for more power.

If anything COVID demonstrated the opposite - governments were all too eager to get back to BAU despite the situation still being severe, resulting in notably high excess death rates.

I think they were tired of defending indefensible policies.

Politicians are experts at that surely. But in this case I'm not aware of a case where any epidemiology or other public health policy experts were telling governments lockdowns needed to be ended. The cynical side of me suggests that there were too many at high levels of government who felt that lockdowns impinged on their ability to enjoy the levels of power they were accustomed to that, and so the opinions of those whose job it was to advise on such matters simply got overridden.

Absolutely false. If the government is going to abridge my rights, such as forcing lockdowns or vaccinations, they better show me the necessity and efficacy of those abridgements. The government can't just come in and say, "This is a crisis, we get to do whatever we want." Fuck that. That's how authoritarians are born. Many closet authoritarians took advantage of covid to become dictators without any evidence of efficacy of their mandates.

That's a theory for countries without a Bill of Rights to practice.