It's not to prop up the Nasdaq. In the doomsday scenario referred to above, housing prices dropping 30%, salaries went down 25%, etc. This is unacceptable to the Fed and they will do whatever it takes to counter this, including dropping as much money as possible.
And they can go negative interest rates which would be crazy, but it's happened before, and currently going on in Japan.
It seems like home prices are pretty high historically in a lot of places, not just a few.
They've bubbled up again not only in SF, but also in most every single area with job growth - SoCal, the whole I95 megalopolis, Denver, SE Florida, Dallas and Austin, Minneapolis, and the Pacific Northwest.
In fact, only parts in the rust belt, South, and Midwest remain affordable, based on historic standards. Unfortunately, the majority of job growth is not in these areas.
I do not see how homes can retain their value when Boomers begin dying and down sizing, as they own the majority of wealth in real estate and the next generation is loaded in debt already and not forming large households at the historic rate.
And they can go negative interest rates which would be crazy, but it's happened before, and currently going on in Japan.