If one has the option to borrow at 0% on a currency that they believe will experience inflation, why would they choose to borrow in crypto (unless trying to short the market of course).

The current problem seems now that just not enough people are willing/able to do anything productive with capital, leading to a shortage of lending opportunities. In theory this should create a buyers market for anyone wanting capital, and to some extent it has. The problem is that, for whatever reason, people choose to poor capital into unproductive assets (IMO crypto being a minor culprit compared to real-estate or share buybacks).

At the higher level, I see this as a consequence of globalisation, where capital was made hyper mobile, and therefore it was applied away from home. Negative interest rates are a somewhat desperate attempt to put more capital in motion at home, but other policy has made this unattractive for anything but speculating.