I agree mostly...

also let's be real it wasn't a 'murder' it was an assassination

I used to call these assassinations but since putting politicians in the bottom tier of occupations during Trump's administration, I don't really use the special term for them anymore. It is murder, just of a government official (current or former) to shift power and influence

They did not want him winning

If I recall, Abe had already stepped down from being Prime Minister (due to "health problems") for what was about a year. But he held a lot of influence over the public, like Trump, because he actually was trying to fix the problems Japan was having while keeping the focus on the nation. It's like putting an old man in a retirement home, sure he has some issues but is mostly fine, and then putting him to death because he talks too much to people outside and motivates them to be better.