Plausible!

I had a bachelor's in physics a decade ago.

But here's how my memory describes how we discovered, or at least how we did it in my computational physics class.

You have stars of known size, and there for light output as its directly proportional to size. You also have a known distance.

You can then calculate how bright the star should be. But its wrong.

Meaning there's things in the way thats blocking light.

So we call it dark matter because it hasn't been directly observed and its clearly there. It could be our fundamentals are wrong, but that's unlikely.

It could very well follow gravitational fields, and then attracted to galaxies with large masses.

But it could also be something in the vacuum. We just have no evidence to suggest either way.