IIRC it was an internal problem that stopped Sato from continuing Nadesico and Stellvia.

For me Xebec is not a choosy studio. For example they are the one that did Toraburu, which is how they do make most of their money, and they also do animes like Occult Gakuen and Azure no Fafner, where they spend these monies on. So it's kinda unfair to blame them on Stelvia and Nadesico's problem