Alternatively, did Wisconsin public retirement funds make an enormous investment in AAPL right when it was about to become insolvent and had no other real options for raising money? That is, you can assume anyone investing in that circumstance (like Citadel into Melvin) would demand a huge stake in return.

As was reported, the capital raise Melvin received wasn't 30% of their total AUM even after the GME losses. And even if it were, it was also reported that Citadel and Point72 received non-controlling revenue share.

I'm having trouble finding specific numbers, do you have a source?

As far as I can tell they started the year with ~12.5B AUM, and have lost ~30% on the year and received a 2.75B cash infusion from Citadel et al, which I assume was at a discount given their position. So my rough estimate is around ~25-35%, given the uncertainty around those numbers.