The fundamental problem with PoS

In regard to PoS:

how does the strongest validator know that his solution (the way he verifies transactions) is the best without going against a hardcore difficulty? Does this validator think he can mess with the work of a whole community?

This is similar to the following example:

rich guy buys his diploma in construction because his university likes him (cuz of his wealth). He does not know much but he is simply wealthy. Now he wants to build something and ofc it is crap because he did not earn his diploma.

That is PoS in a nutshell.

=> More computation equals more work and more work equals more security.