You cannot really compare tournaments and cash games. Like mentioned earlier it's like comparing apples and oranges. They both have their pros and cons. The variance in multi table tournaments is HUGE though. Bubbling several tournaments in a row can be very soul crushing.
If all the smart players played cash games then only rake would be winning in the long haul. There are plenty of smart players that play tournaments. Like mentioned before there is plenty of things to consider during tournaments: ICM, fold
equity vs scared players, position + big stack to steal chips from the smaller stacks, knowing when to call, raise, fold at certain stack sizes WHILE still considering ICM factors. Playing heads up, 3 handed, when you make it to the big money stages of a tournament.
Cash game is a whole different beast. You're dealing with rake for each hand, tipping (live), 3 barrel
bluffing and not having to worry about ICM suicide, making the RIGHT EV+ decision every time, and etc. Usually cash games also play deeper so you will see a lot more speculative
hands in the mix. It makes calling a 100 BB shove a hell of a lot harder decision when you only have top pair compared to 10 BBs.
I'm ranting, but each version of poker has its unique circumstances. If tournaments were full of less intelligent players, then all the smart players should be playing tournaments.