Earlier quoted context omitted.
I think its less an ad bubble and more like something similar to government use it or lose it spending. There is a sort of global hot potato/musical chairs thing going on. No one wants to be the first or last one to cut their ad spending so its a stand off. I've looked at some ad spending stuff at companies in the past and while their official numbers always "added up" there always seemed to me to be huge logic gaps…
This doesn't happen enough. Past 10-15 years or so, thanks to tech overwhelming them, Marketing depts have lost their way. Its not their fault. They get all their training from google, youtube, fb etc on how to think about these systems and when things dont work out the usual reaction is, but we are just doing what Google/FB told us to do.