The device had no conceivable military value, but what it did do was to demonstrate the the West that the 'Sloika' design was viable and weaponized. The layer cake which Sakharov and Ginzburg instigated had no theoretical upper limit on yield.
The concern over the test, and the uncertainty over the effects convinced the bomb technicians to remove part of the uranium tamper to detune the device to approximately half its design yield of 100 Mt.
As it was, the shockwave went round the World seven times, and the blast was visible from over 600 miles away.
By the time it exploded though, it marked the beginning of the end for large weapons. The fourth power law means the less accurate your weapon, the massively bigger it has to be to achieve the necessary military objective. Hence smaller, accurate weapons were paradoxically more effective, and the more of them you could launch on a single bus. You just needed to invent GPS.
So they did.