The Clippers just acquired Norman Powell and Robert Covington, but they are still reportedly looking for a point guard. Meanwhile, Luke Kennard is probably going to lose some time to the new acquisitions.
Clippers get:
Josh Richardson
Dennis Schroder
Celtics get:
Luke Kennard
This gives the Clippers a "playmaking PG", which they supposedly want. Meanwhile, Richardson is a two-way wing who might be a better fit with Powell going forward than Kennard would be, and is under contract next year for when Kawhi and George return. For the Celtics, they get the sniper they need to knock down the volume of open looks that Brown and Tatum can create. The deal saves a little money for the C's this year, and a little for the Clippers next year, so it's a relative wash financially. The Clippers have an open roster spot, so there's no friction with the 2-for-1 players.