[0] https://medium.com/@N/how-i-lost-my-50-000-twitter-username-...
You are dependent on your vendors, period. Choose them wisely. This is not a mystery.
You aren't dependent on your vendors if you can switch them out without destroying your company. The real mystery is why people turn their own businesses in to little barnacles on the skin of behemoths and expect to not get brushed off.
But ICANN, which is responsible for the entire hierarchy, expected that eventually at least some of the new gTLD registry operators would fail, and so there is an escrow agreement for each one. If the gTLD is popular enough that somebody else will operate it, the last daily backup from escrow is given to the new operator and things continue from there. I guess your new registry operator may set fees or other conditions your current registrar doesn't like, but if you like the new you can move to a registrar that's OK with them. The list of names in the registry doesn't vanish unless both your registry AND the third party escrow company screw up.
If the gTLD is grossly unpopular, it may not be possible to find a new operator for that gTLD registry. I don't know what happens in that case, although whatever it is by definition won't happen to many names.
I also don't know what happens for the very stupid gTLDs that are essentially for private use by a single organisation, like .kerrylogistics. And I don't really care, so long as the fees roll in to pay for everything. Actually I'd have billed them for their original request, .kerrylogisitics [sic] as well, but I guess someone felt that was too mean.