Many times, when a bay area company IPOs, a number of people suddenly have a lot of now liquid wealth. (well depending on lock outs in 90 - 180 days) It is not uncommon for those people to want to get off the rent/mortgage treadmill and they will convert their stock into a house because stocks go up and down, but buying a house for cash means you always have a nice place to come home to. And that drives up prices as houses are already scarce.

After Twitter and Facebook IPOs, there were bidding wars between home buyers that resulted in some homes selling for a million over asking price.

I believe the parent is talking about a bunch of people getting substantial liquidity events, and therefore having more money to chase scarce housing.