There's a national pop festival here which is broadcast on TV; for years I've noticed there's always a high-end Moog synthesizer on the main stage, even when the act only plays guitars... it's just product placement.
To be fair, many bands will use automation through midi or otherwise to "play" synthesizers without actually physically playing them. Normally you'd just see them playing the raw audio as part of the backing track but i could see big money arena bands with fuck-you money doing it with real synths live.
Musicians get paid to use gear. I don't know of any moderately famous musician for whom that isn't true.
My favorite examples of this are bands that have that cool Rickenbacker sound and shoot a couple of videos with them. And then suddenly once they get some traction, they're playing Telecasters in public all the time.
Fender paid them. And that's totally fine--musicians get paid garbage so any source of cash is good. I just wish the musicians were more straightforward about it.