Why htop shows 48 sleeping processes while "show processlist" shows none? (MySQL 8.0.21-0ubuntu0.20.04.4)
Solution 1:
Does the account you use to execute the show processlist statement have enough privileges to show any processes that belong to users other than your own ?
Also consider at the OS level (background) MySQL processes and threads need to run even when MySQL is not actively processing any queries. You might look at the threads table in MySQL to see those.
So killing what you see in htop is bad idea.