The Russians managed to do it.
Are their scientists better than yours?
Did they get a head start?
Did they cut corners? Is Sputnik unsafe?
Or is it political?
The Russian vaccine has not completed its phase 3 trials, which are considered key in demonstrating the safety and efficacy of a vaccine and are usually completed before regulatory approval is given.
https://www.businessinsider.com/germany-warns-putin-russia-coronavirus-vaccine-has-not-been-fully-tested-2020-8