Building a business around online ads is a race to the bottom as the younger generation does not buy what they're advertised but instead what's advertised by people they follow. Ad revenue was never enough for twitter, and people acting like they were doing any better under previous management are uninformed at best.

The userbase will exist (growing or otherwise) so long as the platform does. They don't care whether its profitable or not. If he wants to turn X into another wechat/wepay for US or a Line competitor for Japan, then ad revenue is a low priority.