I've watched the Clippers a good amount. Its a lot of things:
1. They don't really pass the ball a ton so their offense can get somewhat stagnant.
2. They've been injured a lot so a lot of shuffling bodies around and this leads to unconnected defense
3. They aren't particularly good at rebounding (especially on defensive glass), at forcing turnovers, or keeping opponents off the line. This means that they're pretty reliant on other teams missing on any given night.
That's pretty much it. They still have the 6th best point differential per cleaning the glass.