Yeah, professional baseball is a high-risk occupation for brain cancer.
Like "as mad as a hatter" in our vernacular, we hear "as cancerous as a ballplayer". Lewis Carroll even wrote about "The Cancerous Rounder" in 'Alice in Wonderland'.
Who said he was exposed during baseball games ? Do you know every bit of his life — where all he went and what he was exposed to ? You are clinging to some cult nonsense and you will disregard anything that challenges it.