Those are network switches, and this is 100% standard practice when decomissioning network equipment. Any time a data center is dismantled you see every single switch like this.
The reason is because every one of those runs was custom cut to length, so they will be useless in any other rack/ facility layout. Also, they all need to be pulled back through the length of the run. If you leave the RJ45 on the end they will not only not fit through a tight restriction, they will grab every single fucking slat on the cable race and cling on for dear life.