Same as if a grad student wins the Prize: Credit will go to the tenured manager of the lab where he worked and the grad student might get their name on some related publication.
It's a bit sad that the original purpose of the prize is lost but that just reflects that we're past the age of lone genius contributors making a difference. No one person really matters. You can replace that grad student or PI with another and the machine will still chug along.
Likewise research is so competitive/redundant nowadays that there are always multiple labs vying for the same results. If we lose any particular lab we will be set back at best a few months.
(For another example from history, despite the vast contributions by Newton, even if he didn't exist, we would still have discovered calculus at approximately the same time frame)