Secondly, the "you invited them, it's your problem then"-attitude of successive Greek, Italian, Serbian and Hungarian administrations, who instead of detaining illegal immigrants all sent them on their merry northbound journey.
There also were threats of sanctions and various kinds of pressures on these countries.
Along with dismissal regarding the various issues coming with it. Italy, Spain, Portugal, Greece, Serbia, etc... didn't want them for a variety of reasons, but let them in and had them transit to the northern "golden paradises".
Only Poland, I think, took measures to prevent the flow from reaching them or even going through. Which got Poland to be treated as a pariah state, with threats of sanctions enforced by Brussels:
Countries that risk undermining the Migration Pact will be met with legal consequences, Brussels has said in a pointed warning to Warsaw. #EuropeNews
www.euronews.com
That European "Pact" didn't appear for no reasons and out of nowhere, but rather as a legal frame work to rein in countries that don't want to tow the line on immigration.
The bloc’s migration pact, finally agreed after a decade of talks, is already in peril as states outdo each other in efforts to get tough
www.theguardian.com
"Being in the talks for about a decade".
Though not EU's doing, the migration crisis still is, in a way, as it was allowed to happen through and unofficial collective agreement. Letting the migrants in was seen as "the right thing to do", with lots of emotional blackmail to push the pill down. So, the EU might not have done it, but it sure didn't do anything to prevent it either despite calls for it... is there a term for "being complicit of inaction"?
Remember that story about the photograph arranging the body of a dead kid in order to get that one good shot?