Maybe, but even monkeys such as their employees understand basic business, and basic business is making money. They're making money off this clown, and therefore it is a good idea to keep him around.
He wins most of his own auctions, so does ebay still get their cut of the final value? Of course they do. There's no skin off their nose in keeping him around. That's why they "found that there is not enough evidence".
If they were serious, I don't know how much more evidence they'd require. Evidently, they're not serious, and are merely humouring you.