The event costs is embezzlement -the donations were taken with a promise they wouldn't be spent on that, and paying for the event means paying for content for his channel, paying to promote his channel, paying to expand his subscriber base, etc.

Compare it to a non-charity event on his channel. He makes content, he takes the money from subscriptions. A "charity event" would then be when he makes content and instead of taking money from subscriptions, he donates it. If the "charity event" is still him making content, and him still taking money from subscriptions, then that's more like a non-charity event. Even if a donation is made with some of the money then the event is still a non-charity event in the sense that he said he was donating the event itself, i.e. not being compensated for it - if he's being compensated for the event then he didn't donate "the event", he was employed for the event.