... my mother, and his wife of 75 years, died at home, probably of COVID-19, although that was not on her death certificate.
In early January 2020, tests for Covid did not exist, except for in China (who has still withholding the virus' DNA sequence from the world), so she would not have been tested. In 2021, she would almost certainly have been tested. If her death cert said nothing about Covid it almost certainly was because she had tested negative.
Both of MM's parents were advanced in age. The Father was in the hospital with Covid, and the mother was not allowed to visit him because that was still hospitals' policy in early 2021. BTDTGTTS - my family couldn't visit me in January 2021, either. The loneliness and worry was probably too much for whatever else she had going on healthwise.
As for their not being vaccinated, blame the "public health" people who persuaded Pfizer not to request EUA
until well after the election and Goobernor Noisome, who F'ed up vaccine distribution and restricted vaccine availability very narrowly in December 2020-March 2021.
Had Pfizer's vaccine been authorized 3-4 weeks earlier and Goobernor Noisome not F'ed up vaccine distribution and restricted vaccine availability so narrowly, maybe MM's parents would have gotten vaccinated and maybe their immune systems were still robust enough for it to be effective. Or maybe, like I'm sure many DU members did, they would have bought into
LIEden's & Kammie's claim the
Bogey-Trump Vaccines could not be trusted to be safe and effective. For my part, had I been able to receive the Pfizer vaccine in early December, I would have, and though half-vaxxed, I might not have gotten Covid, and if I did, probably would not have had to be hospitalized.
Alternate history is uncertain at best, and sometimes is mental

.
I do not know what MM's parents would have done had Pfizer's vaccine been available to them in early December, nor how well their immune systems would have responded.
I do know that I would have gladly received the vaccine, were it available, in early December. I had been following Covid vaccine news since February 2020, i.e. an informed decision in which politics had no role. I also know, because of a recent antibody test, that my immune system would have responded appropriately. Thus, I think it very likely that those "public health" people's and Goobernor Noisome's political

bear much blame for my having to be hospitalized, if not for my getting Covid at all.