Of course there is one reason why there's spent so much money in F1: because the teams think it's worth it. Huge car manufacturer's think it's good publicity, others do it because they want to win.
But why is there so much more money involved in F1 than in, say, sports cars? There are huge car manufacturers there, too, but everybody is happy to spend less. You might say that many sports cars are production based, but there are prototypes as well. But the factories are smaller, the staff numbers are smaller. Even with Peugot, Audi, Bentley and Toyota fighting for Le Mans wins, the racing was much more cost efficient.
But apparently the manufacturer's think that it isn't the "race" that has to be good, but the publicity. Audi thinks winning Le Mans a gazillion times is enough, but others seem to disagree and be willing to spend more in F1.
So is it the manufacturers who brought all the money into F1? Perhaps a part of it, but not all of it. There's more and more money spent in football as well on stadiums, players and everything. But there's no 'manufacturer' involved. And the teams as well don't do it for publicity's sake (in contrast to F1 they are probably more dependent on fans coming into the stadium, although the ratio of direct fan-spent money for tickets and merchandise to sponsor and TV money certainly has changed a lot in the past 20 years as well). Nevertheless expenses have exploded there as well.
We have to think of the Bernie factor. He thought the trademark 'F1' makes money. This is a kind of postmodern way to think of F1. Not the races are important. Not the fans are important. What F1 is isn't important. It is what it represents to those who want to invest money that is important.
But what came first? Those with the money? Probably not, as they could have gone elsewhere. Bernie's need to do business for the business' sake? Well, he didn't invent F1, but he has invented F1 as a trademark. Why does the trademark work? There were always many people that followed F1, but maybe never as much as in the 2000s. Does the trademark work because they are so many fans, or do we have so many fans, because the trademark works?
So in the end, is it the success of F1 that lead to its commercialisation and maybe its demise? Quite funny.... so stop watching F1 so I can enjoy it

Who can untangle this web of manufacturers, Bernie, fans, trade mark and maybe a little bit of sport?
a.