~snip~
After then, my friend forgot about joining the forum and stop trading after got scammed by unknown profile in telegram and the teacher became a successful trader Lol
Every evil for some good (at least that's what they say). Different people have different opinions when it comes to cryptocurrencies, so some will be fascinated with technical things, others with trading, and others only with long-term investing. The teacher made a good move, and the question is why your friend didn't follow her example.
~ to encourage him join the community i explained how he can earning money by joining a signature campaign
I wouldn't call this " joining the community", unless you mean the community of spammers. The sad reality is that the great perks of signature campaigns make many people join Bitcointalk for the wrong reasons.You're certainly right about that, but I have no doubt that a certain percentage of those who came here only for profit have realized that the forum is much more than a sig campaign. Even today, many people come to this forum for the same reasons, but apart from the fact that it is very difficult for them to advance in the ranks, they can only dream of the pay rates that existed in the days of mixers.