using BGP means that within a few minutes of something like that most traffic would have simply started routing around the problem using alternate routes, however cognent is known for the fact that it provides cheap (as in price, as well as quality) transit so certain cheap ISPs almost entirely use cognent or at least use cognent for a large portion of their bandwidth, either by overiding the BGP routing for force traffic to go over cognent to save money (rather than letting it take the quickest route) or in some cases they simply don't have enough alternate bandwidth to cope if they lose the cognent connections.
With any luck those ISPs will be effected enough by this outage that they will revise their ideas and start using BGP properly with multiple transit providers, although the sorts of ISPs that use cognent like that probably care more about price than reliability so probably won't change anything... but users on those ISPs can hope at least...