But since this is considering 'excess' deaths, wouldn't any there need to be an explanation for the temporal increase vs baseline for any non-COVID causes that would explain the excess?
Indeed, but they don't always peak over the same period. Any alternative theory has to provide a plausible explanation for why all these other causes of death (which presumably were also causes pre-COVID) all of a sudden decided to spike/ramp up and periodically surge again (against the pre-COVID baseline).
Your first point would be a contributor to a surge coincident with lockdowns, although even for that cohort some/many of those would not have occurred straight away but may have occurred outside that time window (though accelerated).
None of your other points, regrettable, discomforting and painful though they were, could have caused that surge in excess deaths.
I get that you hated the lockdowns. I’d argue most people did, but that doesn’t preclude the fact that many of the people that hated them also accepted their ‘necessity’. I put that in quotes because the necessity itself may be arguable, but the fact that many people were convinced they were necessary is not.
Well. All animal studies on captivity show negative health effects. All human studies show that stress has negative health effects, and that exercise and time spent outdoors have positive health effects. To the extent that being sedentary and stressed contributed to obesity and/or high blood pressure, there is certainly a plausible causal mechanism worth further study. Additionally, there is evidence of increases in reckless driving — see https://insurancenewsnet.com/innarticle/new-data-reveal-reck... — and domestic violence — see https://news.harvard.edu/gazette/story/2022/06/shadow-pandem... .
Whether they were the right policy call or not, it's clear that drastic environment changes had drastic behavioral effects, and that the behavioral effects either provably did have, or, based on all available scientific data, probably could have had a regrettable impact on excess deaths.
As societies across the globe engage in introspection on COVID response, it's worth further research and factoring the results into their conclusions.