It is a bizarre move. The UK now has one of the strictest entry regimes in Europe, one of the lowest case rates and highest vaccination rates.
Germany allows arrivals from far more countries which are liable to pose a greater risk than Brits. But I partly blame the UK Gov putting out scare stories before the facts are known. It now says the Indian variant is more transmissible and it largely seems the vaccine works against it. But they briefed for weeks beforehand that it was a disaster, would overrun the system and put us back where we started purely to back their domestic message. No surprise when other countries follow.