[ekjhgkejhgk]

> Maybe they already had an account with that domain years ago and are trying to log back it.

This wasn't "log back in", this is a new account created.

> Or perhaps it is just some random spammer creating linkedin accounts with random email addresses

This is what I imagined, but I don't understand why someone would do this.

> Or perhaps the email doesn't actually come from linkedin and it is a phishing you to click though

No, these emails come from linkedin.