That is what happened.
> Some of us trusted that "two weeks to slow the spread" was the sensible policy and what our governments would follow.
Western governments largely did follow that policy, but the US was never able to get out of free-fall. So COVID policy became a bang-bang controller of lockdowns, then slight reopenings, then more lockdowns, because there was never a two week period where spread slowed enough to materially change the risk landscape.
Even when there were lulls in the second derivative, limited re-openings resulted in enormous case spikes. If our numbers ever reached DE or NZ levels, we would've been back in offices and schools. And, in fact, I had plenty of conference calls with Germans who were sitting in their offices last summer.
The re-opening criterion didn't change (except to become more liberal over time, the exact opposite of your characterization). What happened is that the lockdowns -- for whatever reason -- never got spread under control in the USA. That wasn't true everywhere.
> irrational panic
On April 1, 2020 there 26K new cases in the USA. One year later, on April 1, 2021, there were 77K new cases. Vaccination rates among at-risk populations were starting to pick up, but nowhere near where thy are today.
What is the rational policy that would call for lock downs in March 2020 but not in March 2021?
> some would argue...
And others would argue that the expectation that a pandemic should last exactly and only two weeks is its own rather extraordinary neurosis.