One of the main problems of quasars is: How can an energy equivalent to 100 times that of a normal galaxy, be produced continuously in a region smaller than the Solar System? To solve this puzzle, it was suggested that quasars were not at cosmological distances, but much closer, even within our Galaxy, although their redshift indicates that they are the farthest objects in the Universe. This controversy lasted for decades, but nowadays the evidence in favor of distant quasars is overwelming, so that understanding their fantastic power remains a challenge. Another suggested explanation was that collision with other galaxies was delivering extra amounts of gas to the central engine, large enough to sustain a quasar. But further observations revealed that a lot of quasars appear to reside in undisturbed galaxies (see http://www.stsci.edu/pubinfo/PR/96/35.html#Photos). An alternative explanation is provided by DeLightS model on the grounds of a decreasing speed of light. The main expected effect of time decreasing values of c on quasars is that as light slows down, the Schwarzschild radius of the black hole powering it will progressively increase. This will allow accelerated engulfment of material from the accretion disk; so should feed their axial jets of fast particles, increasing the energy emissions in all wavelengths in such a outstanding way. Furthermore, as the black hole mass increses, so does its radius, so that each of these effects helps each other in a synergistic way that allows a natural explanation of such a fantastic power output. Moreover, DeLightS implies that the amount of energy released by matter desintegration would be very much bigger in the ancient Universe than now. The amount of energy to be released per unit of mass absorbed should be roughly proportional to the total energy of that mass, and would be much higher if the well known equation E=mc2 is to be used with a higher value of c. As the Universe grows older, c decreases more slowly in DeLightS model, and the black hole expansion also moderates, and so do the radiation emissions. Then we observe AGN of moderate activity and finally ordinary galaxies with low nuclear activity even if their central engines are bigger and heavier than those of their preceding AGN. Weak or eventual quasarlike activity, such as X-Ray emission, in nearby galaxies indicate that they usually have dormant quasars in their centers.