Look at his stats, he loses the ball alot - he's not good at hold up play. He's a big target for a ball in the box but knocking a long ball up and having him hold up the ball to wait for support isn't his game. Big difference between being a target man and being able to hold up the ball... generally target men are good at holding the ball up because of their size and strength but Benteke's stats for it don't make good reading. Even if he does manage to hold it up, he can't pass... his pass completition % for the season is just 66%.
If all you want from the main man upfront is a good finisher who is quick with good movement... Hernandez? Why spend £30m+ on a lump? LVG wanted more from his striker, so why go for Benteke? You want a 30 goal a season striker, that's not Benteke. Benzema - yes, Kane - maybe (see how he does is his 2nd season when defenders know how he plays).