Because she never had any children in her life and had strange maternal instints towards migrants, "mama Merkel".

Its not really understood by anyone how Germany or anyone living in Germany benifited from the waves of migrants in 2015. Its often said that the migrants were suppose to work to pay for old Gemans pensions, but as only about 3% of migrants manage to get jobs this is proven to be a false assumption.

Clearly as a politition she saw it as a potential vote winner. Also it was an attempt to assert herself as a leader in the context of the EU overall....it could be ventured to speculate that she hopped that a ripple effect would take place with other countries adapting the same attitude and taking positive steps to take migrants and migrate them into their relative societies.

Again in the wider context there is less of an impact on Germany taking migrants given the size and scale of the country and it's economy. As the EU economic leader and powerhouse it's industry based economy could absorb large numbers of emigrants than lets say it's southern european neighbours who until recent times were suffering unemployment rates in excess of 20% and high youth employment rates too. This has in the past week seemed to have possibly reached a point where such rates will not grow again - Greece this week reported a signifiant drop in unemployment rate for example. Migration is now more under control than it has been

Angela Merkel would support the big migrant wave not only in 2015 but also in other years because her convictions reflect European solidarity with migrants and refugees. However this is not possible because there are many legislative limitations that arise in case there is uncertainty of the procedures related to accommodating the refugees once they are in. Therefore if anyone would like to see European political leaders in future making same steps as Mrs. Merkel did back then it is necessary that the country is able and prepared to accept the incoming flow of migrants.

At the same time, external factors such as increased terrorist threat, disagreements among global leaders on the issues of top importance do not allow a leader of a country-leader in the region a great degree of flexibility. Unfortunately seeing the concept of otherness growing throughout and within European countries would not allow leaders to make such brave steps. However, if there is a change in Doublin 2 policy which could compensate for the lack of aforementioned flexibility as the countries who neither have conditions to keep many migrants, nor feel it is fair that they should keep this burden in Europe, would support policies that modify or even council Doublin 2