This happens frequently enough that I think it's worth writing about this on my blog. Every so often a friend will reach out to me about someone I happen to be connected with on LinkedIn, asking to make an introduction. 9.5 out of 10 times, I don't actually know that person.
The truth is since high school (when I first made my linkedin profile), I have been generously connecting with people on linkedin that looked interesting in hopes of finding an internship. While I never found an internship off linkedin (scraping hacker news and emailing people had much hit rate 2016 - 2019 era), many of those people ended up becoming somebody. And now I just happen to be connected to a lot of those somebodies on linkedin that I haven't actually met or worked with.