The free telegram signals are mostly a bait, those groups use those signals to bring newbies to their telegram channel and then try to sell something to them, they may claim that they have paid signals which have a better accuracy or they can the signals earlier and make more profits with them.

But as you state it is nothing more but a scam, they do not really care if you become profitable or not, and even if you do you, you can be sure that it is not really because their signals were effective but it was simply a matter of luck, but once they find out about it they may try to use you to become their spokesperson, as you will really believe on their signals since you became profitable, even if it had nothing to do with them.