To me, pre season rankings are about what looks good on paper. That may or may not translate into a good team, but when you look at the players coming back across the board, Wando and Lex look good on paper. NW has Kropp and Enzo, as well as some other skilled players, but losing the entire defense keeps them out the the #1 spot for me.
And Irmo, what does Irmo bring back that even puts them close to the top 5? I can think of a good number of teams that look better on paper than them.
I will say that upper state seems to have more of the top teams this year. Not so much from a ranking perspective, but more from a title shot perspective.