It was originally a Mac title!

AFAIK Mac is a type of Personal Computer. As long as games would not be locked to console with joystick being only option I would be happy.

Not exclusively. While Bungie was primarily a Mac developer, and Halo was announced at a Macworld, it was always going to be released for Mac and Windows.

It'd probably still be an RTS and likely never become popular. There might never have been a second Halo.

I thought Bungie gave up on the RTS concept and made it a shooter before Microsoft purchased them.

I haven't heard that, but I don't remember much about Halo at that time. I do remember when Halo RTS was revealed, Bungie was talking about how they were sick of FPS games after Marathon and wanted to do an RTS.

Just checked wikipedia. Bungie changed from an RTS to a "third-person action game" before Microsoft came in. Microsoft changed it to an FPS.

When was Halo a RTS?

Remember that one of Bungie's flagship titles was an RTS series called "Myth". Bungie before that had made a proto-Halo FPS series called "Marathon".

When they made Halo, they made a pretty good architecture for showing wide landscapes/buildings/vehicles and large-enough numbers of troops onscreen at once. During the alpha experimentation with the game, apparently they seriously took a look at using this to make an RTS (albeit one really outside of the usual starcraft mold), rather than a FPS.

see here MrScruff: https://www.youtube.com/watch?v=0vTDwW3H5Jw