Dang. A number of really small factors star poping up in these situations. You need nearly perfect farm, meaning long games really hurt S+ chances since your unable to sit in your lane and farm.
Kill participation also becomes an issue. You’d need at least 80% if not more.
You basically have to have spent an entire items worth of gold on control wards to make sure you’ve got a high enough vision score. I joked around with my brother he could just buy control wards and place them on spawn to rapid fire grow his Vision scare. (Btw, not sure if this actually works or not).
Not sure this was the deciding factor, that 1 death. Having 0 deaths and a high KDA and KP is HUGE when earning S+. It means you made big plays and executed so perfectly you never died. I know the system loves 0 deaths as one of the largest extra boosts towards something like that.