All my three Mazdas ('14 Mazda3, '16 Mazda6 and '17 CX5) have the same issue.
The radiator fan keeps going for a couple minutes.
We don't drive them aggressively.
This is very normal if your drives are long enough for engine to heat up.
Don't worry about it.
They have been doing that since new.
No issue with coolant or anything.
All three do it because it's a super known issue on almost all mazdas... Won't hurt to get it checked.