Why the user who blackmailed me then does not give me the negative trust?
Because he admitted he's also a scammer. His negative trust is worthless.
Why the guy who blackmailed me used a "disposable" telegram account if he did not give me the negative trust?
Because he probably does this a lot and his account gets reported and banned.
Why did both users use the same link?
See my reply here:
https://bitcointalk.org/index.php?topic=4452379.msg39826636#msg39826636Why the negative trust came right after my rejection on telegram?
Maybe the telegram user alerted DT members to your scam, or maybe it's coincidence. Either way, irrelevant.