I'm not sure
I'm not sure the trend is quite as it seems. Isn't it more the case that some big companies are more in trouble than others? So fashions and politics are changing so Facebook and Twitter (for different reasons) are in trouble and here we see PayPal cutting back but that may simply be that it no longer offers the advantages it once did. Some years ago I used it a lot as it was an easy way to pay but now I often use my credit card directly as more and more sites (at least those where I buy stuff) offer that as an option.
My point is that these companies and the likes of Google have problems that in some ways are quite specific to them and not necessarily a simple reflection of the market for IT professionals.