Why does a President decide to become a President for life, a Dictator-President?
Simple, power intoxicates and corrupts people; it is human nature.
Democratically elected leaders worked hard to get elected, after getting elected they rapidly fail to remember why they ran for office or the people they are representing. This is where they start to believe that they are entitled to their position.
That is when they go wrong:
First, they remove any legal checks and balances, moving against free media ownership; then, they rewrite the constitution abolishing their term limit, in the hope that their authority, legitimacy, and term will never be disputed. And finally, they make bad but popular decisions to win over the people and their vote, this is when they fuck up!
“No oppression is so heavy or lasting as that which is inflicted by the perversion and exorbitance of legal authority.” - Joseph Addison