It is actually the bitcoin of privacy-- it has the mind share and the technical chops to deliver a solid product.  It has the development team that no other coin can match, except Bitcoin Core.  Etherreum's development team isn't as good as the Z.cash one.

It may be having a run up because of a whale, or it may just be speculation-- but the truth is, everything is speculation right now, even bitcoin.  Actual day to day use of these currencies far lags their price rises.

There are no alts that do the Z.cash job as well as Z.cash, except its clones, and thy all suffer the same way litecoin suffers in bitcoins shadow.

I don't know what you mean about "special interest centralization" but having a good development team is a good thing-- it means keeping up with bitcoin core, for instance (look at how bitcoin unlimited is doing such a poor job of that, while z.cash is porting cores improvements over reasonably quickly.)