At the peak of the last recession, foreclosures boomed and the need for multi-family "workforce housing" increased dramatically.

Boom, there's your cash buyers list.

This is all new information to me but it sounds like the huge boom we have seen in Real Estate the last few years can be partially contributed to the QE of the government after the 2008 crash. 

I agree with @Alan Dickson - there is already a refinancing boom, and the Fed lowering rates again today will only accelerate it and extend it.

In the wake of this COVID19 situation do you think that the Santa Clara County Tax Collectors Office would push out the due date (April 10th) for the second installment of Property Taxes?

The area is super booming.

It coincides with the boom of the Denver market, and leaves out the basically flat year we had in 2019 and early 2020, which would harm the CAGR you impute here. 

Case, case, cluster, cluster, boom.

I've waited so long to get into this and finally when I got my ducks in a row...BOOM.

As mentioned, while the Corona Virus is the primary news with a lot of unknowns around it, service sector workers will be effected, but I think it will bounce back once people are free to leave their houses, and actually booming for a few weeks after lockdowns are relaxed.