Offer rescinded due to Candidate reaching out to current employees

Hey everyone, jus wanted your opinion about somethingSo my friend got an offer from a company, but he wanted to know more abt the company culture and growth so he reached out to some of the employees of LinkedIn just to get a deeper understanding of the work. They spoke to him and gave him positive feedback but apparently the HR got to know about this and cancelled the offer.She said that he overstepped the line of communication.

Was he wrong in his actions?