BlackRock's CEO is not pro #bitcoin he is just doing marketing for the product he expects to sell soon. Why sell it? He thinks it will make him money.
If he had a change of heart and became one of us, BlackRock would already have bitcoin in its treasury reserves. They don't. If they did, we would know. They are publicly traded and required to disclose something like that. That is why we know about $MSTR and $TSLA holdings.