assumed that providing Kiev with the required ammunition and training would lead to victory

I actually do not believe this for a second. My understanding is that the actual higher ups wanted to engage Russia in a war regardless of the outcome plus the ammunition/training part is just the military industry enriching itself. If anything, I think they were actually overly optimistic about Russia turning into a sort of an international pariah and the effectiveness of the sanctions imposed on them, both of which did not pan out at all.