BGP (the protocol underpinning the internet) is built entirely for avoiding outages of any size.
Even email has a method baked into to the protocol for handling failure.
Fallbacks are good, baking in resiliency is better.
BGP has its problems (that time centurylink blackholed traffic but wouldn't drop their connections, bgp hijacks etc), but it's not centralised in single (or very few) points of failure
ps. "The Internet was build to survive attacks" is not true. It's a myth made popular by Robert Cringely in the early 1990s. The Arpanet was simply a protocol for mainframes used by computer scientists to connect. The Internet is relatively resilient against attacks, but that was not the "whole idea". It was not in the design at all.
Bob Taylor: “In February of 1966 I initiated the ARPAnet project. I was Director of ARPA‘s Information Processing Techniques Office (IPTO) from late ‚65 to late ‚69. There were only two people involved in the decision to launch the ARPAnet: my boss, the Director of ARPA Charles Herzfeld, and me. The creation of the ARPAnet was not motivated by considerations of war. The ARPAnet was created to enable folks with common interests to connect with one another through interactive computing even when widely separated by geography”.
Vint Cerf says the same about invention if TCP/IP transport protocol.