This is untrue, entire eastern EU screamed like crazy against such immigration when she started importing immigrants en masse, "wir schaffen das". France faced the same with entire communities from Maghreb, most didn't work, 0 integration even after a generation or two spent in Europe, they knew language only if it was also their native one. Nobody in the east wanted that, entire political blocs before elections formed on opposing this and other fun EU moves (remember banning regular lightbulbs without good-enough LED replacements in
entire EU market? Pepperidge Farm remembers... Or cutting down most of Borneo ancient rainforest to have effin' EU-subsidized bio fuels that ruin car engines quicker? Same story, I know this is EU but Germany is by far the strongest voice in and these are typical merkel moves - big moves regardless of consequences and picking up pieces later).
East had no prior experience with migrants due to living for decades in effectively prison camp guarded by soviets, no travel or other exposition to other ways of life. We were very monolithic cultures (and still mostly are).
The voices were completely ignored and overruled by behemoths like Britain, France and most powerful voice in the bloc - Germany.
Don't revision past, I lived through it, saw masses of people getting absolutely mad pissed off and feeling helpless and unheard with arguments which over time proved them mostly correct.
I don't hold those opinions myself, some of our best friends are muslim immigrants but oh boy go to the eastern EU without camera and ask random folks on the street outside capitals, or just listen to them. Or look at election results, this gave russians and their constant influence very good arguments since they position themselves as 'guardians of traditional family values in society', regardless of how its true or not (clue - its not but thats detail here).