Let's be real, the MVP almost always goes to whoever scores the most points. It's the same reason in football the MVP often goes to a quarterback who threw a lot of touchdowns. It's why the MVP in baseball used to almost always go to the guy who hit the most home runs. In recent years, thanks to advanced stats and sabermatrics in baseball, the MVP has shifted its dynamic, often taking into account all facets of the game.
Whenever the sports writers who vote on the NBA MVP decide that they are sick of LeBron winning MVP, hey Derek Rose, they just go with a guy who had a hot scoring hand. With Westbrook, he had an absolute mental season. He deserved the MVP after doing something that had never been done. Harden had a good year, but he mostly coasted on being the best player on a team that didn't have anyone near his level of talent. There is a reason that Russ and Harden score so much, they don't have anyone else on their team who is a legit and consistent threat. With the arrival of PG and CP3 respectively, that should change, but both guys are typically viewed as being bad with the ball. Just because you put numbers in the assist colum, that doesn't mean you are good with the ball. Just because you turnover the ball a lot, that doesn't automatically make you bad. Both guys have a reputation for shooting bad shots too often. If you run the offense, as both guys do, but you've made up your mind before the inbounds pass that you are going to shoot no matter what, that is a bad decision and makes you bad with the ball. If you refuse to pass, that makes you bad with the ball. If you spend too much time trying to dribble or try to constantly get to the basket, that makes you bad with the ball. Both guys do all things.
Being good with the ball isn't just about assists. Getting an assist requires a fair amount of luck, because you are dependent on the other guy making the shot. Then there is the whole making the pass that sets up the assist argument. In hockey, you guys can assist on a goal. I'm not 100% convinced that basketball needs to adopt that, but being a good passer is about more than just assists and being good with the ball is about making smart decisions when the ball is in your hand.
And just scoring a lot of points doesn't make you good. Look at all the college players who topped scoring charts then were total busts in the NBA. Scoring 40 is nice, but there is such a thing as shooting your team out of the game and Russ and Harden have both done that. Derek Rose did it in the playoffs the year he was MVP. Kobe did it a lot post Shaq.
If you prefer a fast and loose high scoring style of basketball, that's fine, but no team is ever going to win a title with Russ or Harden as the focal point.