Upwards of 70% of the "refugees" are fighting age males who have left their wives and children behind to fend for themselves. The government is welcoming them in, even though they are bringing a wave of crime and rape that is horrific in its proportions. What could possibly be their motive for this? In the refugees own assessment, they are committing jihad by migration. It's the way that Islam, as a political ideology, has always functioned. They entered a state as refugees, then took over either by force, or by causing the citizens to assimilate to them, not the other way around. They don't assimilate. They conquer. Just read their writings and listen to what they are saying.
News reports suggest that around 1,000 men of "Arabic or North African descent" engaged in violent and sexual attacks against women on New Years Eve. While it is true that the government allowed these men to immigrate to the country, Germany has been allowing Mideastern immigration for generations without an attack of this magnitude. These men acted on their own accord. If they had behaved themselves in the streets of Cologne, this wouldn't be a story because nothing would have happened. The chief of police has been relieved of his duties and Chancellor Merkel is calling for tougher immigration laws, which point to the German government showing concern for stemming any additional attacks. They certainly didn't cause them.
Though the German government could have done a more efficient job on the handling and management of the Cologne attacks on New Years Eve, it is not correct to say that they are solely to blame for the events. The individuals that committed the horrific crimes in Cologne are, to put it mildly, the scum of their country, and deserve to pay the penance for their actions. At this point, the only concern of the German government should be catching as many of the perpetrators as possible and administoring the justice to them that they deserve.
The government can't be held responsible for the narrow views and simple minds of bigots and fools. No matter the situation, those will strongly held negative beliefs will always be the first to act. They act under fewer inhibitions and with greater assurity that they are correct and they need only show the rest of us how right they are for our understanding to grow.