Did you read the whole article? Sure sounds like racism to me. The lynching wasn't just about rape. It was about rape allegedly committed by black boys against a white woman.
No, about 1/3 to 1/2.
I agree that racism was a huge part, I doubt they would have lynched a white person.
But despite that, them stopping after hearing a declaration that the black person was innocent just amazes me, it doesn't fit into my understanding of lynching which I always associated with just simple hate, i.e. "grab any handy black person and kill them".
The article also mentions how many black families had fled the town and how they were ready to get another teenager. That's how the "grab anyone" part works. And it's definetly racism.