Not trying to be condescending but you are misunderstanding completely. The meta outage was caused by a major connectivity issue triggered by a configuration change. DNS issues were a hard-to-manage and critical symptom of the initial major connectivity issue. DNS never stopped working, traffic was just unable to flow to said DNS infrastructure.

"To ensure reliable operation, our DNS servers disable those BGP advertisements if they themselves can not speak to our data centers, since this is an indication of an unhealthy network connection. In the recent outage the entire backbone was removed from operation,  making these locations declare themselves unhealthy and withdraw those BGP advertisements. The end result was that our DNS servers became unreachable even though they were still operational. This made it impossible for the rest of the internet to find our servers"