Come on man. We both know that's not the reason. If we were looking only at attendance in April, you may have an argument there.
It's culture. I put it on paper before, but the Padres shifted their culture on a dime, and fans responded. Now, I do grant that, because of San Diego's loss of the Chargers, it does offer a more unique situation to much more swiftly capture the attention of, and build upon, their market. But I see no reason the Twins couldn't do the same thing eventually.
Downtown San Diego is much nicer than Downtown Minneapolis, but the population that lives within walking distance (2.5 km) is not hugely different - 72K to 62K. Granted, Minneapolis is not walkable. (Thanks terrible urban developers.) But Downtown Minneapolis employs a lot more people than San Diego.
Idk, this is just me researching on the fly.