There have been people who proposed both exist, and they also proposed a way on how they interact. I think you misunderstood the question entirely.
It's not about EITHER mind or body. There's a difference between semantic nitpicking and complete misunderstandings.
the significance of the question arises from problems with what mind and body are, and how they could interact.
Descartes tried to conjure up a strange idea where the mind is a spirit that has enough strength to make a gland in the brain move, controlling the body.
Leibniz said the mind and body DO NOT interact but have been perfectly synchronized since their dawn.
Malebranche straight out claims every time the mind and body do something synchronously it's God who intervenes.
etc.
For them, it was a matter of figuring out how they connect. For others it's different altogether.
going for dual aspect theory is probably your safest bet.

that must've been horrible. how'd you end up in that?
And ye. It's this that makes me stray away from idealism and possibly also dualism. The brainstatus affects us a bit too much to simply be separate...
scary.