GP actually did speak in terms of per capita numbers (hence "population share"). In absolute numbers, California would exceed Florida in old people; as shares of the population, California has (according to your second link) 14.3% of their population over age 65, while Florida has 20.5%. This works out to be Florida having about 43% more old people per capita than California. If the claim upthread that deaths per capita in Florida more than doubled that in California is accurate, then 43% more people 65 or older per capita does not explain more than 100% more deaths per capita.
> Guess what STILL less than California. Guess what positivity rate at the BOTTOM of all states.
As to your positivity rate point, I can't confidently speak to whether your argument would be valid if the data was as you said, but your data is not accurate: your link lists Florida at the bottom of all states, but it also lists them as having a 0.0% positivity rate. The latter is, unsurprisingly, not correct, and neither is the former. Going through to its listed data source [1], I calculated positivity rates (number of positive results / number of total results) for each state using the data as of October 11 [2] (filtering for "date" equal to October 11 of this year).
Using cumulative numbers ("total_results_reported"), Florida has a positivity rate of 10.4% (18th highest), California has 5.7% (44th highest). Using new results with a date of October 11 ("new_results_reported"), Florida is doing better than earlier: only 4.6% positive (42th highest). Still twice California's 2.1% (53rd, below every other state and every US territory, but ahead of the District of Columbia).
1: https://healthdata.gov/dataset/COVID-19-Diagnostic-Laborator...
2: arbitrarily picked to be far enough back I could be sure I would not be missing data for some states due to reporting lag on the first try.