No. "Obesity" and "vitamin-d deficiency" can't explain what happened in Italy (a lot of sun), and also can't explain what happened in the Nordic countries (much less sun), including Germany and Sweden (the later having order of magnitude more deaths than the former, measured as the percentage of the population). Sweden is particularly bad, having the deaths per capita even worse than the U.S. the last time I've checked.
What we see is that countries that were lucky enough to do strong enough prevention actions early enough had order of magnitude less deaths than those who didn't do them (and Sweden is in the latter camp, even if they did have more response than most admit -- they did close all universities, for example). The scale of deaths seen in New York would have never happened, had the use of masks been common early enough.
Eidt: Regarding "vulnerable populations" Italy and Germany have similar number of "vulnerable" and it seems Sweden would be better than Germany then:
What we see is that countries that were lucky enough to do strong enough prevention actions early enough had order of magnitude less deaths than those who didn't do them (and Sweden is in the latter camp, even if they did have more response than most admit -- they did close all universities, for example). The scale of deaths seen in New York would have never happened, had the use of masks been common early enough.
Eidt: Regarding "vulnerable populations" Italy and Germany have similar number of "vulnerable" and it seems Sweden would be better than Germany then:
https://commons.wikimedia.org/wiki/File:Population_pyramid_o...
https://commons.wikimedia.org/wiki/File:Population_pyramid_o...
https://commons.wikimedia.org/wiki/File:Sweden_population_py...