Another obvious key is that our defensive ends play defensive tackle.
But it cannot simply be that we are undersized throughout.
Recruiting size is not difficult. At all.
Actually, recruiting quality size, especially DTs, is very difficult in college football.
And I get your athleticism over intelligence argument, but unless you are recruiting freaks like USC or Texas, you've got to have a good mix. Even those schools have to have mostly sound players. Athletic players who constantly get out of position on the football field will be taken advantage of every time.
K-State coaches don't want to get fired. They are going to play whoever they think gives them the best chance to win. Period. Now, those decisions probably at times are wrong, but almost every decision made by college coaches (including Snyder) is to try to win football games.
I'm not so sure recruiting size for the DL is difficult. I'll go find some guys, they won't be super talented, but they'll be big and adequate. Is it possible big and adequate is better than small and adequate? We always go small/slow and smart. Maybe try big and dumb? Both are flawed, maybe one works better than another. It probably depends on the individual.
The biggest problem in sports is that coaches think that because we've been playing a game for 100 years that every philosophy or attitude has been figured out and there is no reason to try to do things differently. So, Joe Bob Clements and Chris Cosh may be 100% sure that they are playing the right player at a certain position, but I'm 99% sure that they haven't tried enough options. Does the linebacker position need to exist? Why do basketball teams need a small person that can dribble the ball and pass well to be on the court? Maybe try 5 guys who can jump and are all over 6'9"?
Kansas State requires innovation because we cannot compete otherwise.
Let's not forget that a lot of college coaches, especially assistants, get to where they are mainly by "paying their dues." That is, they start by playing, then become GAs, then lower-level assistants, etc. A lot of these guys, while perhaps intelligent for a football player, are not all that intelligent in the big scheme of things.
Would explain why, when you get someone who is actually halfway intelligent (ie, Mike Leach), they are heralded as football geniuses and clown a lot of other coaches.