Space Marines in giant suits came from Starship Troopers lol. The novel was about mech suit marines fighting a war against space bugs and blue aliens with energy weapons, and the marines were led by religious officers.
Protoss aren’t elitist space elves (which cmon, warhammer 100% “ripped off” from Tolkien) and they have like three religious schisms happening at the same time, along with a false homeland right of return & persecuted minority group thing goin on.
Zerg were Tyranids before Tyranids were Tyranids - if anything GW “stole” the Zerg aesthetic for later editions of tyranids! Plus, the idea of a bioweapon species attaining sentience and wanting more from life is waaaaay more interesting than “bug who wanna eat errything”
And ultimately, who cares who “steals” what between giant corporations. Unless it’s individual artists or small entities getting fucked over, IP protection is a fuck. It’s a matter of personal taste, but I think OG Starcraft had some pretty cool ideas!
Often times developers would model units & characters physically in clay, rotate them to capture pics from each angle for isometric projection, digitize them & make sprites out of them. They look like toys because they’re basically actual toys! I think Diablo & Starcraft used digital 3d models turned into 2d sprites though, rather than actual models.