If you hit someone then you are at fault. Very few scenarios where this isn’t true such as is someone cuts you off and brake checks you and you manage to catch

If you hit someone then you are at fault. Very few scenarios where this isn’t true such as is someone cuts you off and brake checks you and you manage to catch it on video and can prove it. Otherwise if you can’t stop in time if the car in front comes to an instantaneous stop you were too close and are at fault. None of the what if they have Brembos brakes matters if you can’t stop in time of an instantaneous hard stop you are at fault. At required safe distances the car in front can hit a brick wall and you should have time to stop. There is no complication here.