The weak point of every tank is the bottom and the top, because those are least vulnerable in the combat for which tanks are designed, so they can be left way less armored. But long range 155mm artillery gun or a well placed mine hit exactly those parts. Note Soviets tried to take care of the roof at least by having round turrets, but all the modern NATO tanks have flat roofs since they never before had to fight when enemy had air or artillery advantage, they literally forgot it can happen.
The weak point of every tank is the bottom and the top, because those are least vulnerable in the combat for which tanks are designed, so they can be left way less armored. But long range 155mm artillery gun or a well placed mine hit exactly those parts. Note Soviets tried to take care of the roof at least by having round turrets, but all the modern NATO tanks have flat roofs since they never before had to fight when enemy had air or artillery advantage, they literally forgot it can happen.