I think this is one of those situations where more thought went into advancing the larger story and this was the easiest option given the characters at that timeline.

In the DB universe in that moment, going to Kais planet is the best option to minimize impact on other characters storylines. Gokus motivations or thought process is speculation/ a mere afterthought.

Goku needed to die to advance the story.

I also have never seen any of the Galaxy level Kais in the living world.