By who (or is it "whom"?)?
Ground Proximity Warning System, most likely..........
There is some pilot on youtube that went through the radio transcript that was released. IIRC there were 8 warnings, all automated I think.
Some guy by the name of Captain Steeeve:
https://www.youtube.com/watch?v=Xm6G7EOP5Qc
At 1000’ elevation they got a warning because the plane wasn’t configured the correct way (stuff like speed, wing flap positions, etc.)
Then more warnings 15 seconds later, 25 seconds later, etc. Each warning they were supposed to pull up and fly around and get back into the landing pattern. The youtube guy said those automated warnings are mandatory to go around - not just a “hey, you’re a little too fast - just wanted to let you know”.