Why Littlefinger bothered to kill Jon Arryn and assassinate Bran Stark?

Jon Arryn have already known too much about Lannisters' incest, so I would expect that he will be killed by Lannisters or someone else for sure.

Also why bother to kill Bran Stark and frame Lannisters when Lannisters would already have motive to kill Bran Stark and silence him for good? Wasn't Littlefinger's plot wasted to do it all by himself when it could be resolved in a way he wanted without his involvement anyway?