Trump also touched upon Musk's failed attempt to purchase Twitter.
"Now Elon should focus on getting himself out of the Twitter mess because he could owe $44 billion for something that’s perhaps worthless. Also, lots of competition for electric cars!" the former president wrote.
Musk committed to buying Twitter back in April, but spent the past several months trying to back out of the deal. He formally gave up on purchasing the platform earlier this month, citing concerns about the number of bots and fake users.
Some analysts interpreted this as Musk making excuses, and Twitter launched a lawsuit against him this week.