what I don't understand is how paying for YT ads can be profitable. I've never clicked on a YT ad _intentionally_ nor I know anyone who did, having asked a few people. I admit the brand awareness works tho.

There's a counterintuitive effect sometimes, which is that the person who tolerates a stupid ad is also more likely to buy the product. This was used by email spammers whose messages came littered with deliberate grammatical errors as an efficient filter against too-smart targets.