Ahh, that's a systemic issue; a system where an undesired outcome is inadvertently incentivized. Aka an emergent phenomenon.

No recorded direct link of communication. The CEOs and half the board will individually go to company paid lunches with competition, members of the board are straight up members of a competing board. Or even lobbyists and lawyers of competing companies going to events together that happens daily.

"But I pinky promise we don't talk about our competing business plans while we eat lunch and golf together"

I think most conspiracy theories are bullshit. Especially things that require mass government, academic, and/or inter-industry coordination just cannot happen easily due to the fact that large scale coordination of people is very very difficult.

But in a market with 2-4 long-standing players in an oligopoly with offices right by each other, you bet your ass there is in-person collusion... it has been caught many times and likely the extreme vast majority of cases are not caught. Price adjustment is extremely easy to collude on and has mountains of excuses of plausible deniability and "just following the market" bs. So far, there has yet to be a market that has remained competitive and hasn't turned into an oligopoly. Monopoly is the steady state of a capitalist system without strict anti-competitive regulations.