I would argue that it's about the status of mathematics, and that Mathematical Platonists are necessarily substance dualists - so include modern thinkers like say Max Tegmark (eg his book The Mathematical Universe). Popper with his Triplism is basically a Dualist also.
Logical form, including mathematical form, involves abstraction: that is identifying a type of similarity that has substrate independence. That's like how a piece of computer code can run on more than one computer. Is the abstraction, the code, then independent of material instantiation? No, it absolutely isn't. But you can see why people get caught up with the idea it is.
Descartes was a substance-dualist. He believed in two seperate realms or modes of being, the extensible physical world, and the 'inextensible' world of ideas and logical forms. In his own lifetime, Elizabeth of Bohemia basically devastated this argument in her letters to him, and is widely credited with demoralising him into an early death. Her points on the problems of substance-dualism stand, see the Stanford Encyclopedia of Philosophy article on her here.
I would argue modern science is property-dualist, believing in one substance that has two -so far- unreconciled faces: mass-energy, and entropy/information. It was widely expected the latter was just arrangements of the former, and so emergent from 'material' reality but work in quantum-gravity, like Loop Quantum Gravity and Universal Constructor Theory seem to point to information or arrangements as being fundamental, with mass-energy as emergent from it.
To understand substance-dualism, look to the status and origin of mathematics. I argue it's a viewpoint that implicitly 'haunts' modern science and obscures the distinction between property- and substance-dualism, because of Plato; who founded The Academy and so Academia, by blending Socratic Dialogue with the math-mysticism of Pythagoras. The special status of math is still widely held by serious people, and I would argue continues to rely on Pythagoras-like mysticism that cannot hold up to close scrutiny.
My views on the origin, status and reasons for utility of mathematics, as arising from intersubjectivity and shared experiences of the geometry of solid bodies, here: https://philosophy.stackexchange.com/a/92064/30474