Stinkingly, many of the migrants have smartphones; that enables them to navigate unfamiliar geographies, making alternative plans when their original routes are closed. And it provide instant messaging from other migrants as to the current situation, political trends, places to head for, and places to avoid. This has lead to unexpected developments.
For example, while Europe tried hard to ignore the situation in the hope that it would either go away or at least not get much worse, the steady drip of distressing images and the lack of resources to regions having to deal with the newly arrived immigrants, eventually prodded Angela Merkel into making public statements welcoming refugees to Germany's metaphorical shores. At the speed of light, the change in mood was disseminated around the world, triggering new waves of migration and completely overwhelming those European governments in the front line. The situation hasn't been helped by the fact that most are relatively poor by European standards (Greece, southern Italy, Serbia, Croatia) and others are led by right wing xenophobic governments (Hungary and Austria both fairly reactionary polities).
Unable to cope, peripheral European states are putting up fences and closing their borders, leaving thousands of migrants stranded. Despite the worsening problem, Europe bickers, the rest of the world treats it as someone else's problem and Ban Ki Moon pontificates while the UN does nothing. Not a moment we will be able to look back on with admiration as notable for its compassion, statesmanship and leadership.