The Future isn't looking bright for the Lakers
Think about it. The Lakers will have to rely heavily on Anthony Davis post-LeBron, to lead them into their next era. I don't see that going well, mainly because he can't stay healthy. He also had limited success as the number one option in New Orleans. Based on that, Los Angeles could be in serious trouble if they have to depend on him more when he's in his 30s.
In fact, there’s a decent chance that Los Angeles will be terrible later in the decade while the Spurs could be contenders. However, armed with those two picks plus their own, San Antonio could continue to add lottery-level talent, even as they potentially compete for championships.
For the Lakers, giving up assets to get off of Westbrook is going to hurt, but turning a negative player, with an awful contract into two good rotation players on good deals makes a lot of sense for them. Additionally, they'd receive Langford as a throw-in, but as a former lottery pick, he could still turn into a decent rotation player. It's a win-win.
Ultimately, the Lakers and the Spurs make sense as trade partners, even despite their decades-long rivalry. Los Angeles will look to offload Westbrook this summer when they’ll be able to throw in an additional first to try and find a taker. San Antonio could be that taker.