My family and I were just a few seats ahead of this passenger. He was calm when asked to leave by a delta employee, but perhaps a bit unsurprised, asking just “should I take my bag?” when asked to leave. I didn’t see law enforcement on the plane. I did overhear someone say “why didn’t he just go to the bathroom?”. Could he have been doing something he should not have been doing in his seat? Unseemly behavior (& likely illegal) may be a reason to divert a plane to throw a passenger off, especially nowadays.