They did not reduce the speed of light to zero, that would destroy the universe as it is currently observed. What they did was slow down the wave/particle that is light in a controlled labratory experiment. The purpose of this was to learn the basic nature of the universe without resorting to “god did it.”
"It's a real first,'' said Stanford physicist Stephen Harris, who collaborated on a 1999 experiment with Hau that slowed light to 38 miles (61 kilometers) per hour. "These experiments are beautiful science.''And as I mentioned earlier, it is likely that science will eventually find a way to speed up light (or light particles, if you prefer). The following is from the same article.In the latest experiments, researchers took steps to not only slow light to a virtual crawl, but to stop it completely.
Manipulating light's properties is a subject of intensely competitive research. In July, physicists in Princeton, New Jersey apparently pushed a laser pulse through a vapor of cesium atoms so it traveled faster than the conventional speed of light.
http://www.space.com/scienceastronomy/generalscience/lightstop_010119.html
However, I don't see an indication that the experiments were done with a goal of refuting or evading an explanation of "God did it." I think it was just good old basic human curiosity. Not all scientists perform their experiments with implicit/explicit declarations that God was not part of the original equation.