I'm not sure if that was sarcasm, but I have to disagree.
I think, generally, there's a reason that the same teams seem to do well every year. Those are the teams that care a lot about SO, that practice a lot, and have build up a program over many years. Sure, the influence of a new coach can make a big difference too, but a lot of SO is the "program." The leaving upperclassmen, if they're strong, help to teach the underclassmen how things work and how to do things well, and there's a tradition that people try to uphold.
Of course, a difference in coaching staff and dedication, with a good set of people in a certain class can do that too. For example, several years ago, Welsh Valley had one coach and they went to Nationals several years in a row and even did well at nationals. Then, when that coach retired and the team was handed off, there was a couple of years in transition - even a year where WV didn't make it to states. When I got to WV, we got a few new coaches and had a couple strong grades in a row, we were 2nd at regionals (after getting 11th the year before) and then 7th, then 5th, then 3rd at states. But, still, the tradition of knowing that WV has had experience with really good olympiad teams in the past is part of what made that possible. Now, in the tradition that those few years have left behind, WV still has kept in the top 3 at regionals and top 10 States.
Harriton '10, UVA '14
Event Supervisor in MA (prev. VA and NorCal)