My theory -
I dont know about the US, but the reason for the european and eastern lifters sucess is probably due to not having a choice.
A russian kid with poor parent was doomed to live a short life and working his ass off in the mines, factories or the likes. Hard manual labour, lausy pay and long hours. The one way a russian (or ukrainian, or bulgarian, or ...) kid from the working class could be wealthy and sucessfull was in sports, if one had talent that is.
Thats also the way behind their training, doing hard manual labour long hours from a young age is or was common (I have no idea how these countrys are nowdays, but i think its a bit better), and what was the revard for the work? Food on table and mony for rent. By practicing sports, olympic events in particular, was as hard a work as in the factory, but atleast it gave them a chance to be sucessfull.
Thats my two cents