As I understand it.

USA like NY times lose a bit in simplifying for the kind of audience that would re-elect Trump. 
Your meaning of moderate, may not be their meaning. 

Moderates exist in a 'comparative' sense, even then in very limited way.

Clerics/Ayatollah have the final say, even on who can stand for elections.
They have blocked those who they see as a 'too popular' as a moderate before.
If they are moderate in our sense, maybe, maybe not?

Hardliners naturally advance easily. 

Clerics/Ayatollah control, secret service - security forces, foreign policy, constitutional changes, reform. 
Well-funded religious military IRGC of almost a million to project power internationally.
Basij maybe a million people hold power internally, shoot demonstrators, police public morality, eyes and ears on the street. 
Appoint Judiciary head that controls judiciary. ( No one is challenging power in courts).

A system that assures hardliners proliferate, advance no matter what. 
Probably a great way to advance is to point out colleagues that are soft. 

Religious kleptocracy is a thing, probably old Holy Roman Empire the same. USA going the same way.