unintended consequence
Noun
Meaning
unintended consequence (plural unintended consequences)
(originally sociology, in the plural) An outcome of a purposeful action that is not intended or foreseen.
Examples
But HBO is less interested in how many people are watching than in how much the people who are watching are liking the show. They didn't set up their business model to make writers happy. It's just a nice unintended consequence.