free23
The key difference might be that Signal must be tied to a phone number, while the others advertise not needing a phone number as a feature. Thus, they may be overwhelmingly popular with criminal groups.
are designed to provide anonymity to their users and their features make it tough to resolve the entities associated with them
It comes down to the fundamental difference between privacy and anonymity.
Signal is private. There aren't any secret backdoors (lots of people looking at the code) despite three conspiratorial thinking.
Those other apps are designed for anonymity.