I have an instagram account that I basically don't use, created probably 10+ years ago. At one point I randomly decided to log in and found that my username was randomized and someone else (not even a brand account) was using my original name. I never got any emails about my account being accessed, my password was random, no login activity, etc. To this day I'm still wondering if the account was compromised without a trace or if instagram just decided to give my name to someone else.
Unless your email was also compromised, your name was taken by an FB employee. They do this all the time for their friends and whoever might bribe them.