There's many 'assumptions' from family and friends. Assumptions or insights from people that knew Ruby well? All easily found via GOOGLE. And then there's Tonahill, Ruby's lawyer and Jim Leavelle. One example from Leavelle, whilst escorting Ruby to the Dallas County Jail Leavelle asked Ruby why he did it, Ruby replied:
''I wanted to be a hero. It looks like I fucked things up.''
From Leavelle:
" he just wanted to be a hero. He wanted to have the glory of killing the man who killed a beloved president. Ruby thought he’d be arrested and charged, but he thought the Grand Jury wouldn’t indict him. Or if they did, he wouldn’t get more than a few years. Then he’d return to his night club, where people would come from far and wide to be seen at the club owned and operated by a legend."
From Tonahill:
“Ruby considered himself a hero. He thought he had done a great service for the community."
He even describes himself as a "martyr" in his mind-blowing WC testimony.
If, as it seems, Ruby just acted on the moment, try to imagine the countless hours spent by countless researchers trying to join dots that just don't join. There's a lesson there.