> DDoS sizes have continued a steady climb over the past three decades.

This is a bit misleading; according to Wikipedia[1], the first DDoS is said to have occurred less than three decades ago.

[1] "Panix, the third-oldest ISP in the world, was the target of what is thought to be the first DoS attack. On September 6, 1996, Panix was subject to a SYN flood attack, which brought down its services for several days while hardware vendors, notably Cisco, figured out a proper defense.", source: https://en.wikipedia.org/wiki/Denial-of-service_attack