You know sometimes smogon just annoy me. My god Choice banded chesnaught hits like a truck. Woodhammer has even knocked out garchomps that try to switch into it. Bringing it in on an azumarill means that the opponent either loses there azumarill or switches into a banded hit from this thing which not many pokes will appreciate. Yet for some reason people on smogon are saying stuff like running a non offensive leech seed, spikes, spikey shield, protect set or saying it can't take a hit because of its typing which isn't true because especially physical hits it can tank very well barring flying type moves. I don't know, a lot of the pokemon in this gen that people on smogon have said isn't great have turned out to be a lot better than they say they are.
They're trying to make use of its sky-high Defense stat. I wouldn't have thought of a Choice Banded set either tbh.