All the coaches mentioned was, I think, 3? Clarkson By Dero and Bomber and Hardwick by you? There isn't too many more across the 127 year history of the competition. Ratten's first stint at Carlton put him well inside the top 100 of all time games coached.He won a final the season before he got sacked and they seemed to be on an upward trajectory. I dunno it seemed pretty weird at the time given they had been in the doldrums for so long.
And of course it happens but historically, swapping coaches every 2 years hasn’t yielded much either. All the coaches mentioned to rebut your point had pretty terrible starts.
Leon Cameron, Stewart Dew, Mark Harvey, Alan Richardson...