If anyone encounters this kind of scam and pays a close attention without being so nosy about money they would make, then they can quickly observe if it's a scam or not.

This kind of scams always looks obvious from the beginning, just look at how the guy is explaining rubbish.

There's no proper detailed explanation for what his business of buying telegram usernames entails.

There's no introduction of who he, company he is working with. This is just a normal approach when some people chart you up randomly and if you are smart enough, you would be mindful of such unexpected messages.

Being extremely careful will help in this kinds of situation,  don't be so nosy about the profit you will get, think about the risk.