You don't understand how plaintiffs lawyers think. There are two defendants, so two potential pots of money: 1) Primo, 2) the Spurs. Primo is ostensibly being paid around 4MM this year and 4MM next as part of his extension. So let's say its about 4.5MM after taxes. He can likely shelter a good chunk of that remaining amount, so let's say he'll have about 1.75MM in free funds that could be used to satisfy a judgment. 40% of that is approximately $700,000. The Spurs likely have insurance, have considerably more than $8MM in assets and can't shelter those funds the same way an individual can.
So tell me, why on earth would a high profile plaintiffs attorney actively sever their ability to go after a very deep pocket in favor of a fee that, best case, would contain absolutely no premium? Especially in a high exposure case.