That's one of the reasons but there's also the fact that we had no fucking clue where white people were from and most of the oldest artifacts from before the Iron Curtain were found in the Caucasian mountains. Given that the Hittites were the oldest known and best researched Indo-European group and their proximity to the Caucasian mountains you end up with a bit of a weird bias.

While a lot of this shit has origins in 1800s racism the ones that stuck around did so because of long term misunderstandings. There was also a short lived hypothesis that different "races" evolved from different species of ape, though that one didn't survive particularly long.

It's not our fault, all our standardized tests growing up had us pick that bubble if we were white and it never came up anywhere else.