Is it always the second drivers fault?

If you rearend someone you are responsible about 99% of the time. To say "they stopped to fast" is to ADMIT you were following too close, or not in proper control of your vehicle.

The only major exception to the rule is if the car in front had just changed lanes in front of the rear car, then braked sharply. That tactic is used in the insurance fraud known as "swoop and squat." In that case the second driver has no opportunity to prevent the collision (which is why it is done for fraud.)

In the accident you describe the second driver is at fault for not leaving enough room for the first driver to stop suddenly if necessary. In emergency situations there is no such thing as "stopping too fast."

Usually it is the fault of the following car for following too close. You should leave enough distance so that you can stop in time even if they stop suddenly in front of you.

That said, I've had some close calls where people in the next lane over pulled over without safe clearance AND hit the brakes as soon as they got in front of me so that they could turn right in front of me. If I had not been able to stop in time, it would have been their fault because I was not following close. They made an unsafe lane change.

there has been more than one court case in which judgement was given as second car driving into back of first was not deemed 100% at fault ( in one case was given as 50-50% )

though there is a perception that every following driver should leave sufficient room to stop in an emergency without impacting vehicle in front.! nevertheless it was upheld that common sense and normal anticipation and reaction times etc can be overcome where a person stops very suddenly for no obvious emergency.

eg case in question was a car stopping at a bus stop braking very heavily on a damp road when he saw a Friend waiting for a bus. car behind failed to stop in time causing a collision. judge upheld the 1st car should have indicated and stopped normally and very few would have guessed or expected such an emergency stop to be Carried out on a clear Road during daylight hours with no pedestrians . thus considerably contributing to the collision. ( causing it actually)

Ordinarily, you are correct, but there are exceptions.

For example, the question posted after this one says talks about a driver who "whenever someone gets right behind him, He slams on hos [sic] brakes". In that case, it would be the first driver's fault, because he slammed on his brakes when there was no valid reason to brake.

If the first driver stops too fast on purpose, because the first driver wants to cause a crash, then it is the first driver's fault.

If the first driver stops hits the brakes when there is no valid reason, no stop sign, no car in front, no traffic light, and the only reason to brake is because of the tailgater behind, then it is the first driver's fault.

If the first driver brakes for a normal reason, when braking is really needed, and is not trying to cause a crash on purpose, then it is the second driver's fault.

Your description indicates that the following driver would be at fault for following too close.

But it is not always automatically the rear driver's fault in all rear-end collisions. There are drivers who rush to get in front of you only to stop at the light. It's called swoop and squat. Common insurance scam.

if your car gets hit from behind it would not be your fault unless your playing road rage games and seen doing so

the rear car should travel with a safe stopping distance

If you rearend end someone, you are automatically at fault, no matter how the person in front off you is driving.