I think males of any species, without regard to size, will breed any female that can get to. Bigger bucks may try to prevent it but there are too many females to prevent smaller bucks from mounting a good number of them.
I have done a lot of elk hunting and when it comes to elk there are herd bulls that try to contain all the cows. Problem is as soon as another bull comes along and challenges the herd bull it distracts him and a younger bull nearly always uses that chance to breed one or two cows. Seems logical to assume the same thing would happen with deer.