Is this even possible? By what mechanism could a prion disease become airborne?

Viruses have evolved to more easily infect cells in the respiratory tract for this specific purpose, but prions are much less sophisticated.

It seems there may be some evidence they can evolve, but enough to hijack cellular machinery in such a way that they could increase the concentration in the respiratory tract enough to transmit?

Seems a bit far fetched but I’m no prion expert.