Heard a bit from Shannon Sharpe that is the best explanation I’ve heard. Kawhi saw what happened to Isaiah Thomas and didn’t want to risk his big payday by coming back early.
https://nesn.com/2018/04/why-shannon-sharpe-believes-isaiah-thomas-affected-kawhi-leonard-saga/
That's pretty weak. The Spurs are the most cautious team in the league, they practically invented resting old or injured players (i.e. no injury is too small to sit someone down for). Hard to think back to the all-time greats who have missed time like this, especially if they could have played. If you are on a team that's 30-52 I get it, but Kawhi's impact take the Spurs from a possible 1st round exit to really bad news in the 2nd round for one of the contenders.
And, if it comes to that, zero chance I send him to the Lakers. In fact, I'd send him to the Eastern Conference even if I don't get as much for him as I could in the West. Too bad there isn't a team in Vancouver anymore (yes I know it's Western Conference). Or I'd send him to NYC, let him see what it's like to be under the constant media pressure.