Elon Musk does not understand Bitcoin, several posts he’s made show a lack of fundamentals. Elon is intelligent and extremely capable of understanding Bitcoin, but Bitcoin like all technical disciplines takes time to learn and understand and he has finite bandwidth. 

As you say he is building cars and mars rockets.

Despite his lack of understanding, Tesla still hold 9,720 BTC making them the 3rd largest holding public company. So he has a hedge against inflation.
https://bitcointreasuries.com/

We all assume intelligent experts are experts in all disciplines. This is wrong and we need to stop doing this.

Bill Gates is an expert on software, but doesn’t understand electric cars or Bitcoin
Warren Buffet is an expert investor, but doesn’t understand Bitcoin
and Elon Musk is an expert engineer, but doesn’t understand Bitcoin

This is OK, we have enough experts and you don’t need to be an export to hold or spend Bitcoin.