I don't quite get this, you are saying Erlang is fault tolerant? I'm confused here because fault tolerance is something that the application using a particular language needs to make sure right? Sorry if I mistaken your statement.
Here's a reasonable summary: https://stackoverflow.com/questions/3760881/how-is-erlang-fa...
https://ferd.ca/the-zen-of-erlang.html
It's more about assuming things will fail by default with good ways of handling it built-in at the language level. A lot of people also find its inventor's thesis enlightening. Here it is:
http://ftp.nsysu.edu.tw/FreeBSD/ports/distfiles/erlang/armst...
And for those concerned, there's also at least one project to write the native functions in a safer language to reduce their bugs a bit:
It may be a poor mans Erlang, but better than nothing ;)
Everything is built so that you can operate a telecom switch and never drop that emergency call.
Erlang (Ericson language) is not necessary, you can also program for this in Elixir, although personally I prefer Erlang.