It's caused by he was an agenda for doge coin. Remember that elon was mentioning on his tweet if he needs a crypto that can be used in mars and doge coin is including on his project.
he was also buying lots of doge coins and you must see that there are some addresses that owned more than 50% of total supply.
Elon will not buy something if that will not be really useful for him. The communities have been talking about this since at the end of last year.