I believe the logic with no-fault is that a person who consistently has claims that “weren’t my fault!” is probably either very unlucky or has bad driving habits that invite accidents (like driving in blind spots).
IIRC if A drifts into B’s lane, and B has the dashcam footage to prove it (that A in fact crossed the line) then A might be liable. But generally, B would be liable for driving into C. So often, additional witnesses help. “I swerved because the car crossed in front of me running a red light, and then he didn’t stop”. If witnesses bear this out, then there may be no criminal liability, but if you can’t prove who was the car that caused the accident, odds are your the insurance pays. If they can find the culprit, then your insurance goes after their insurance, and the police may cite them for the traffic offence.
If B brakes and gets rear-ended, then D who rear-ended him is at fault for following too close. however, if dashcam footage shows a deliberate attempt by C to get rear-ended (B slams on his brakes for no reason, or switches lanes in front of D and jams on the brakes) then C is driving dangerously. The car hitting the rear of another is assumed to be at fault, they must be defensive about legitimate reasons for the car in front to stop (i.e. animal or child runs out into the road). The trick is to prove this is not the case, that C was driving in an unsafe manner. Dashcams help.