The IETF picked OSPF. Certain vendors pushed IS-IS onto large ISP
customers, during the mid-90s, in part to give themselves a proprietary
advantage (at the time only 1 or 2 vendors had a solid IS-IS
puhleeze! is-is worked at scale. ospf did not. heck, when most
large isps were starting (late '80s and early '90s), ospf barely
worked at all.
and perhaps one should not accuse a company of a "proprietary"
advantage for implementing a well-known standardized protocol.
but it sure is cheering to see that old wars and old warriors are