The EU is basically pushing for any plan to distribute refugees between member states (and not specifically targeting this or that country) for multiple reasons:
To deal with the sheer magnitude of the Syrian refugee crisis and the great unbalance between destination countries. According to Wikipedia, Frontex counted 1.8M irregular entries in 2015, that's huge. And if you want to “share the load” as it were, you need to find somewhere to send these people.
Germany is already taking a huge number, Sweden is taking even more compared to its population, Spain and especially Italy have to deal with people entering there directly, Greece is completely overloaded, France had more refugees than other countries (even Germany) before the crisis and is participating in resettlement programmes so it can plausibly resist calls to take many more. So, no matter how skeptical you might be regarding their capacity to process and accept refugees, you cannot make the numbers work without including smaller countries and the new member states in central and eastern Europe.
To fix the Dublin system. It was supposed to insulate northern and western member states from an influx of asylum seekers, thus allowing them to lift border checks without completely giving up control on who comes in the country or not. It was put under great strain when people started crossing the Mediterranean following the destablisation of Libya and completely fell apart in 2015-2016.
Some national courts first interrupted transfers to some countries (especially Greece) then the ECJ basically suspended the Dublin system with respect to Greece and now many border countries fail to register asylum seekers or respond negatively to all Dublin requests so that the system is basically dead and needs to be replaced.
To get some handle on the refugee situation in the EU. There is a long-standing effort to harmonize this area of the law, with a string of regulation on asylum, the Return directive, and the Dublin system. Yet, the summer of 2015 saw complete chaos, with trains blocked and people lining up at the border, walking on the motorway or being rounded up. If it wants to avoid completely losing control and seeing member states resort to ad hoc and illegal national solutions (like the border checks France regularly performs at the border with Italy), the EU sorely needs to find something, anything, to deal with the crisis.