this repeated tweets is not from Elon himself, report has it that he was hacked. Elon must would have not lowed himself to this level of trying to pump doge. people are just taking this tweets serious without making findings.
It's possible if elon's account was getting hacked but there's another possibility too when elon gives permission for someone to control his account.
People are too lazy to search about the fact and those people are only caring with their profit from the market. That's why they were taking it seriously as it can give them all very big profit in a short time.