The idea that the planet was physically destroyed, Death-Star-style, is not "likely" at all. The Ur-Quan have never evinced this level of power, nor would that kind of overkill be necessary -- there's nothing about the physical existence of a planet that says that a particular kind of species must evolve there. After all the Dnyarri were killed or changed into Talking Pets, there's no reason to think Glilandy wasn't left as a lifeworld or, at *most*, scorched away into a deadworld. But the idea that the Ur-Quan have the power or the propensity to actually blow up planets is silly.
Also, much of this info belongs in the Dnyarri entry, not the Glilandy entry.