I know that most of it is stolen and jerry-rigged, but with so much time, some of them must have devoted themselves to science like Len and magic. Knowledge is power, and many demons seem to love power. The abyss is mostly devoid of entertainment, so some demons must have decided to expand intellectual pursuits in the hope of permanently improving their living standards for both profit and safety. If somebody down their is capable of making a tv and channels, all others will allow them to live as it would relieve some of the monotony of their eternal lives.
The abyss is one of the least interesting places one can go given enough time due to the unchanging environment, population, and uniformity. Astlan changes at the very least with the deaths of its people. People know that a greater level of knowledge and technology would lead to better conditions for all, which is why I think their is a library in the abyss somewhere. People hate the place anyways and view the exercise as monotonous in many situations. Perfect for the abyss and some knowledge has to be shared to quickly expand it. Keep what you want hidden, but then let others improve the understanding of something so that you might use it later yourself.