Earlier quoted context omitted.
DDoS is distributed denial of service. It isn't coming from one server. It's now trivial to buy 100 Gbps or more of DDoS so sites would need 400G or more to simply eat it.
If you have a single server flooding spoofed traffic, it appears as a DDoS to the victim. It's at this point that the distinction between DoS/DDoS breaks down slightly. It is very much not "trivial" to buy 100Gbps+ of DDoS. I'm highly confident the majority of D/DoS attacks are from single servers, because it works. If you have a 10Gbit server and your target has 1Gbit (or you 1Gbit and them 100Mbit, it still happens…
Taking down a single endpoint that can issue commands no longer stops the attack and the attack is now going through multiple layers of DNS obscuration.
Architecture of a modern DDoS service looks much like any modern geographically distributed production application and network.
Attacks are getting quite sophisticated, and are extremely, extremely cheap.