Unfortunately, I fear the reality of this situation is a lot less nuanced than you're expressing here. It's more likely that the advertisers who give YouTube a lot of money simply threatened not to advertise on the platform should he continue to have a presence there.

In David Icke's case, he directly threatens telecommunications carriers' ability to sell 5G services. That's directly counter to said carriers' marketing goals.

Not to anthropomorphize YouTube too much here, services like them derive their morality from profit. If something threatens profitability, they'll do what's required to correct that problem. Moreover, there are a number of feedback loops in place that reinforce this behavior. This isn't a matter of YouTube judging a bad idea on its merit; this is a matter of them judging a bad idea on how it affects advertising revenue.

Put in a somewhat more uncouth manner: Money talks, bullshit walks.