No, it wasn’t incidental, but was it intentional? Didn’t look like it.
Are you saying he intended to kill him? What tells you he intended to kill him? He was looking and interacting with people filming him. You think he thought ‘I don’t care, I’m going to kill him.’
Manslaughter? Sure. Jail time justified? Sure.
But the jury was aware of the consequences if they did not convict of a charge that didn’t include the word murder.

A moot point since he’ll get a new trial in the future and we’ll see what happens then.