Making investment decisions based on an influential person's opinion is never a sound way of investing because it doesn't always end well. In truth Elon never told anyone to buy BTC or doge but most people bought up these coins because of what they see as a likeness from a top tech guy like Elon.
I also dont get all the outrage because the markets has dipped a lot more in the past and will still likely dip more in the future, irrespective of if Elon tweets in support or against BTC