Beacuse brand recognition is valueable and theoretically they should be able to start winning throphies again, and such, earn a lot of money.

It seems to me most professional sports franchises increase significantly in value over time. Pretty rare they're not worth considerably more in say 10 or 15 years after a purchase. Football, baseball, American football, basketball, etc.... they all tend to appreciate considerably in value over time.

The increase in value is probably more a product of the value of the franchise name and its relative success vs individual players though obviously if they can recruit and build up a lot of successful teams and players that will add even more to the value of the franchise.

The financial performance of the team I am sure plays into valuation but even if they're an eternal money-loser if they have strong revenue overall and continue growth in recognition, product / merch revenue, stadium / venue revenue, etc. etc. it has value to owners.

Nearly all pro sports franchises are hugely coveted by billionaire types, cities, States/countries, and investment groups. Maybe the very worst teams that can't seem to pull together winning teams for decades might eventually not have much value but it seems to me like even the worst teams draw fans and fill seats. The Clippers have sucked for decades but have stayed around forever and have a significant fan base.

I don't necessarily think the economics and math make any sense but it's maybe like the rarefied ownership aspect and prestige that draws investment. Private jets, multiple huge sprawling mansions that the super-rich maintain around the world, super yachts whose value could feed a small country and get used 2 weeks of the year.. I mean the math makes no sense but there's a certain prestige factor that belies that stupidity.

United make 700m per year pre COVID. Things are going back that way slowly.