That of society live by?? upto?? One's??

I am going to guess you meant:

Why is it that the people who are looked up to by society as honest, good people are the same ones who tear down society's foundations and ethics?

To which I would say, sometimes that's true, and sometimes it's not. I don't see any reason to suggest it's always the respected ones who let us down. What is actualy true is that we notice more when the respected ones let us down because we expect them to not do so. So this is registered as the baffling outlier since it doesn't match the desired pattern.

In reality random people let us down, some of them are expected to, some surprise us because they are not expected to.

All people are human and fallible, so the root problem is that we have unrealistic expectations of our heroes -- we confuse that they're accomplished, with that they're perfect.

Because generally pillars of the community are made of clay, not stone.

They have been moulded, not erected!

Because most folks are intellectually lazy sheep and really don't look into the people they are voting for. This is not complicated.