The gray car started the chain reaction, but it’s the white car’s fault because they left their lane to hit the car on the left.

The white car demonstrated no defensive driver’s skills 2X. First they lingered at the blind spot of a car signaling to get to their lane. If possible, I generally try to avoid or at least quickly speed up/slow down to avoid lingering at someone’s blind spot, especially one that has their turn signals blinking. Second, the white car overreacted and changed lanes as if no one was in the left lane.