Yes it is assumed if no other info is available that the car doing the rear-ending is at fault. It is determined that the car in front is at fault or nobody is at fault depending on many scenarios. Below are just a few from AI. BTW- I wasn't the person that attached the laughing whatever you call it pic on your post.
Sudden, Unnecessary Braking:
If the front driver slams on their brakes for no apparent reason, and this causes a rear-end collision, they could be partially or fully at fault.
Malfunctioning Brake Lights:
If the front driver's brake lights are not working, the following driver may not have adequate warning of a stop, and this could shift some liability according to Drake Injury Lawyers.
Sudden Lane Changes:
If the front driver makes a sudden lane change without signaling and cuts off another driver, leading to a rear-end collision, they could be held liable.
"Brake Checking":
If the front driver intentionally slams on the brakes to intimidate or retaliate against the driver behind, they are likely at fault for any resulting collision.
Mechanical Failure (with prior knowledge):
If the front driver's car has a mechanical issue (like brake failure) and they continue driving without addressing it, and this leads to a rear-end collision, they could be held liable according to Steinger, Greene & Feiner.