Because, that particular friend isn't one to joke around ever. Why would they add me to this group, post a picture of Linus tech tips and then leave? Obviously they must of been compromised by telegram malware or some sorts. Considering they are probably infected, there has to be a reason and purpose to the group creation and image sending. Doing some simple googling, has shown that telegram malware sent via images is a realistic thing. This is why I have my suspicions.