Honestly, you don't know this. It is impossible to know this. It is just a weak opinion. Many different permutation of the strength of Mighty Johnson opposition are logically possible.
Remember, GSP fought the same 3 fighters 7 times. DC has only fought 4 LHW guys, but because he fought twice against a Monster, his overall record is being greatly exaggerated. A lot of UFC records are not as strong as the way people talk about them.
Mighty Johnson's dominance is making the MMA community dismiss his competition. Sometimes when something is just that good, one other interesting way we can look at it is by saying the competition is just that bad.