Why do I need a websocket intermediate for a telnet server in a web client?

I’m very new to the concepts of protocols and networks and a project just fell on my desk regarding these topics.
The project is a MUD (Multi-User-Dangeon, one of those old text-based rpg’s that you can run from the terminal).
The problem in it is that it’s using a third-party client to give users a web interface, the client is served by this third-party entity and they give the possibility for us to use their client by passing our telnet server as query parameters in their URL.
Sometimes their server falls down so that’s the job: bring a copy of their client to our own servers (free software, and we’re preserving all credits of course).
When studying their code I realized that in order to communicate to our telnet server, first they setup a websocket server of their own (the address is something like “ws://etcetc.com”).
I got confused by that because, in my understanding, the need of a websocket in this kind of communication is for bidirectional communication between client-server and, maybe, provide a security layer on top of it, since telnet is not able to do so. However, their websocket doesn’t seem to use this security layer (I supposed that from the single ‘s’ in ‘ws://’).

So, if I don’t care about security and telnet is also a bidirectional protocol, why do I care about a websocket intermediate?