Japan has a parliamentary election coming up this Sunday and that is why he was out on the streets giving a speech supporting one of the candidates in the city.
Apparently that visit was only confirmed late last night so how the suspect managed to find out about this and prepare remains an open question.
https://www.bbc.com/news/live/world-asia-62088876
Re: the suspect and knowing where Abe would be
IMO the suspect is part of the cabal, one of their assassins, and the cabal has tentacles of spies everywhere that knew where Abe would be and how vulnerable that location made him.
That poor man, such a savage and brutal crime. I hope they publicly execute the murderer.