How that is even possible? Germany and USA got their own superbomb even earlier that USA in OTL. I would had imaginated that there would had been already for or five other nations which would had possessed superbombs.
During the first generation after the end of the SGW, both the USA and Germany acted aggressively to prevent intervention proliferation, with US efforts directed against the Japanese Empire and German efforts directed against the Russian Empire.
This admittedly loosely-coordinated US-German strategy began to break down in the 1960s, when the new Russian Republic established good diplomatic relations with the US and the US defeated Japan in the Fourth Pacific War. During the 1970s-1990s, there were several countries that developed the capacity to produce superbombs, without actually building them; this was a lingering legacy of the fear of possible US/German preventive actions in response to testing a weapon.
The catalyst in TTL for the final collapse of the international anti-proliferation “consensus” will occur in October 2025, when both Bharat and China, as part of a period of sustained tensions between the two great powers, conduct superbomb tests within days of each other.