SA wasnt beating GS that year breh
Winning game 1 does not mean you're winning the series. They got their kufi knocked off by a weaker OKC team the previous year and that SA team was actually better than the team lost to GS.
Kawhi was on another level in 2017. Look what he did against Memphis, the games he played against Houston, and the brief time in Game 1 against GS. Obviously would have been a tough matchup, but the premise of OP is that LA picked a bad team to sign with. He would have been 3 games from the finals had Kawhi not gotten hurt.