Ross Lyon took that club's soul when he left. The two years with Watters did unbelievable damage from a list management perspective. Richardson's problem was that the Saints rose too quickly (9th in 2016, 12 wins). The frenetic style was never going to be sustainable with Riewoldt/Montagna/Fisher/Dempster/Gilbert - last remnants of the Lyon era - about to retire., a dearth of good senior players in their prime, and list management still failing to produce the goods at the bottom end.
Ratten's an interesting one. Very similar and slightly superior record to Hardwick at the point he was sacked. Started in fairly similar circumstances and also lost his first nine games. Carlton were (briefly) premiership favourites in the year he was sacked, and that club, too, has never recovered.
While Ratten is very astute tactically, there were apparently problems with his relationship with the players towards the end. Grigg, in retirement, lauded both Pagan and Hardwick but avoided mention of Ratten. But until they get their drafting & trading right, nobody can help St.Kilda.