A Ph. D. is an academic qualification
A professorship is a rank in the university teaching cadre.
The two are not related! But a Ph.D. can help one rise up to the rank of Prof.
The two are not indicators of intelligence!
Just like the military ranks, once you make the rank of Prof, you never lose the title even after you retire/resign from service. Eg, when was the last time that Prof Saitoti worked in a university?
Nothing is real unless it can be named; nothing has value unless it can be sold; money is worthless unless you spend it.