Yup, any major sport moved from freeview, lost viewers but increased revenue.
You know what Prem league football viewing figures would look like if the same games were on BBC... but the revenue would be way way down. It's not difficult, BBC, ITV, they bid for it and Sky blew them out of the water. Well in reality BBC won it but offered WAY more than they could actually afford, yet less than Sky could afford, and ended up pretty much giving up the rights to Sky. The number of people watching really doesn't effect the sport in the slightest, amount that each viewer effective pays is the only meaningful metric and F1, football, NFL, whatever, anything that went to subscription based viewing has increased revenue drastically as a result.
1.5billion is pretty huge for a sport with maybe worldwide appeal but only 15-20 races a year. Sky put out 15-20 games a month. For the number of games/races taking place F1 must be up there as one of the biggest money sports in the world, it will never match football/NFL in total revenue purely down to vastly fewer number of games/races on show a year.