Would that explain why Linux is used to develop so many special effects in Movies, not Windows?

Video editing and modeling/rendering effects are completely different toolchains. Tools for the former are still very crude compared to what's available on Mac/PC. Support for the latter is good on Linux, probably thanks in large part to the Unix legacy imparted to the effects industry by SGI.

But a lot of the Linux machines you see in VFX shops are just headless render nodes. People doing the creative work often use Macs or PCs.

Those Linux machines are mostly used as render-farms, i.e dumb boxes to crunch numbers.

You'd have to get their Mac (or sometimes Windows) machine out of the special effects guys cold, dead, fingers.

That said, there are a few commercial offerings for 3D modeling work on Linux, but shockingly less than in Windows/Mac land.