You...don't believe it works like that? Ultimately a sponsor isn't going to pay much if no one watches the spot. Advertising has always involved getting as much data as possible on how your ads are doing.
I don't have any one definitive link that will tell you "this is how it works", but I've picked up a few things from the various discussions I've seen some youtubers have.
Traditionally, we the players paid for the servers. If it was a server browser game like counter strike, the various clans would pay for their own servers. Companies that sold gaming servers would also host some as an advertisement of how good their servers were