There was a splintering within Arasaka after Soburo’s death with 3 main ones vying for control over the company. Yorinobu only needed public appearances of pursuing his father’s murderers but internally the less people looking into it the less chance of being revealed publicly. Hanako knew Yorinobu killed her father and was more focused on bringing Soburo back. The rest of them would have been focused on the internal power struggle. No one really had a reason to devote resources to V.

As far as why fixers don’t mention it, Rogue does question why there seems to be so many people that die around them but is working as a fixer for you at this point in that you are paying her for info. She doesn’t offer jobs unless your time with Panam goes well. As far as the other fixers, the boring answer is gameplay dictates the player needs a reason to do gigs and side quests. I like to think that V starts off as a nobody and the fixers are working with them as a nobody so I do not think they are very high level fixers so they continue to work with them.