Upvote:2
why the Soviet Leader refused to help Afghan Allies in the war against the Mujahideens?
Well, they didn't refuse to provide any help except "foot on the ground". And the reasons they had are obvious if we remember what actually happened.
One may argue that the level of support came out to be unsufficient etc. Well, errare humanum est. Probably they hoped too long that Taraki would sort it out himself.
After all, as we know, Andropov and Ustinov insisted on direct intervention in December 1979. Though even then it was split decision. There's also a widespread opinion that Brezhnev finally agreed on the military operation because of personal matters (he considered Taraki a good friend and was very upset after his murder, so he particularly disliked the idea to cooperate with Amin anymore).