Board Thread:The Flash discussions/@comment-9346948-20171108005845/@comment-3221148-20171111151357

Time remnant is not really "created". It's a person, whose time travel is required to happen, forcibly taken out of their supposed direction.

Imagine you lived your whole life, than a "future you" comes out and says you, yes, you, have to die for reasons, while he gets to live. And if, by chance, you both survive, only one gets to keep your current life. It's understandable why "Savitar" snapped.