Isn't every businessman doing something that makes them profit from it. That's what Elon Musk did, because by popularizing Doge, the price of Doge will be high and Elon certainly already has a large amount of Doge in his wallet.
even though we don't know elon musk's wallet.
Of course, every businessman is always trying to get profits. Elon Musk also got the advantage by supporting Dogecoin. At least, his popularity is rising and people will judge "Elon Musk is a hero in crypto industry". But we can't claim that Elon Musk has Dogecoin, we have no proof about it. As long as we don't really know it, we are unable to claim "Elon Musk has big number of Dogecoin". Logically, if Elon Musk wants to invest in crypto, he must choose the most recommended coin (Bitcoin).
I also doubt that, if Elon had Doge, why? When Doge fell he should have been able to intervene so that Doge would not fall, but he kept quiet, so it is clear that he does not have it. He only uses Doge to seek the popularity he wants and he has already got it.
Doge will not be able to develop if it only relies on Elon, if not from himself and his community, which is quite large, so don't expect too much from Elon. If he wants crypto, you are right, he will take Bitcoin, which already has a reputation.