Not out of goodness of heart, but out of ideological conviction and obligation to international refugee conventions

Please. Powerful countries ignore international conventions at their leisure. Germany included.

Even if the will to have younger blood to fuel the economy is a driver for such a move, it has nothing to do with propping up pensions: in an aging population you'll need people working in your country if you want to keep things running, no matter how your pensions are being paid…

She desperately wanted to avoid "bad scenes" at German borders.

IDK if the book of journalist Robin Alexander "Die Getriebenen" (the driven ones, AKA top German politicians driven by events) was ever translated into English, but that guy had daily access to the Chancellory and describes the situation to a T.

Merkel built her career on media appeasement and an illusion that Germany is in such good hands that nothing untoward can happen to it. It sort-of worked until 2015, when the outside world could not be kept at bay anymore.

Angela Merkel built her career in the GDR under Soviet rule, in case this fact or the eviction of hundreds of thousands of families from their homes in Germany to house those immigrants is of interest to you.

I think she actually did, that and her Christian beliefs. Not all of politics is cynical, sometimes politicians are selfish and unreasonable and act on their principles. There were more fiscally prudent ways for Germany to increase its population for various political and economic ends if Merkel so chose to use them.