> The main reason for IPv6, and its only real reason for existence, was bigger addresses.

Which also allowed for better route aggregation in the core BGP tables.

Better node mobility support. Better multicast support. Genuine link local addresses.

IPv4 had a lot of unfortunate edge cases. I think IPv6's greatest strength and also responsible for it's slow rollout was it's insistence on solving several of these problems at once, along with IPSec as the article notes, and hammering them into the hard requirements for the core stack.