Marketing dollars work, and bidding for ad placement is competitive. The field is made of clever people that optimize it. However I think it's dangerous to believe that advertising is "numerical" or metrics can fully predict ROI of advertising - the same way subprime mortgages weren't numerical, and the same way a population mortality graph cannot predict coronavirus.

A sudden drop in revenue may adjust the economy of bidding and show a potential bubble. The tiny budgets and one click campaigns (with platforms inventing unique metrics & targeting woo) in social media marketing compared to traditional marketing (huge barrier to entry) feel like penny stocks vs traditional stocks. You can easily mislead individuals and tiny businesses.