I would assume methodological flaws. Just by looking at the number of authors and the publication date, the authors simply did not have enough time to control f

I would assume methodological flaws. Just by looking at the number of authors and the publication date, the authors simply did not have enough time to control for area-specific factors for 191 countries and 252 subnational units. Finland reported 53949 deaths from all causes in 2019, 55488 deaths in 2020, and 57343 deaths in 2021. (The figure for 2021 is preliminary.) The total increase from the 2019 level in 2020-2021 is ~5000 deaths, and a large part of that is explained by aging population.