Having lots of first-round picks isn't nearly as valuable in the NBA as in the NFL. There is a lot more player performance variation at the top of the NBA draft than the NFL draft. You would much rather have the #1 overall than five first-round picks between 10 and 20.
Trading away the #1 overall, with a player perceived to be a potential star, is extremely risky. The LA Laker pick cannot be the #1 overall, per ESPN. So they are trading the #1 overall for #3 and another high, but not top, pick.
>>>>In NFL comparison, would you rather have one Peyton Manning (#1 overall) or two Ryan Leaf's?
It's great that they have two likely lottery picks next season in Brooklyn and LA, but they already had the Brooklyn pick.
There is probably some benefit in pushing the assets out. With Durant in Golden State, it looks like they have a solid five-year window to dominate. If you could trade a #1 overall for a certain #1 overall in three years, it might make sense to try to load up for a run when the GS stars are in their mid-30's.
It certainly does give the Celtics more ammunition to compete and be an exciting team.