Not all creations that look cool are meant to be. Such was the case for the Soviet Union's tank that was boosted by a rocket engine. This allowed the heavy tanks to propel forward without being stuck in mud or difficult terrain.
However, regardless of how bold the system was it wasn't considered safe enough, nor was it affordable, so it was scrapped.
Why would a tank use rockets?
Tanks are used to travel across uneven and difficult ground, heading off-road and on dirt paths swamped with mud. Tanks are better-suited for crossing uneven and sometimes muddy ground than regular vehicles thanks to their tracks, which lower their general ground pressure per square inch.
That said, in times of battle like in WWII, even some of the best tanks would get stuck in the mud.
Rockets could have been the answer the Soviet Union, known for its ingenuity, was looking for as they can boost a 40 or more ton tank forward and out of the mud. Sounds ideal in theory, but in practice it's another story.
The main issue here is the danger that surrounds having a rocket-backed tank during a wartime situation. Any shot from the enemy could get through the rocket's skin, setting it and its cargo off. Moreover, as these rocket engines were seemingly fitted into T-55 tanks, as per the video, these tanks apparently weren't able to throttle its speed or direction. In essence, the crew would have just pointed the tank in the vague direction they were aiming for and triggered the rockets.
That's a problem for a number of reasons. If there were any big rocks or wooden terrain, let alone water, on that path, the tank and its crew would have been in a major conundrum. Another probable issue would have been the cost of attaching rocket engines to the Soviet Union's tanks. With tens of thousands of tanks, it would have most likely been unfeasible to afford them.
The rocket-powered tank never came to fruition, but it was a noteworthy idea at least.