It's a self-cleaning corporate rolodex.

It solved the long running problems of: a) keeping tabs on people across company moves b) a public, standardized CV

Its moat is the scale of its network. Very, very hard to replicate, massive cold start problem. It killed business cards!

Maybe some AI generated thingy can attack it, akin to Grokipedia vs Wikipedia, but man is that unproven. Zero incentive for users to switch.