CNBC Struggles Even as Financial News Abounds
CNBC's ratings are flagging, with daily average audience down 25 percent in second quarter from 2001 period, despite spike in big financial stories; network also faces question of whether it shares in taint of now-discredited stock analysts and chief executives it helped make celebrities; CNBC executives say they are making comeback; note they have shifted away from treating trading day as sporting event by offering deeper economic analysis; parent NBC chairman Robert C Wright says rating losses have not seriously hurt profits and reflect loss of general-interest viewers, not businessmen and investors sought by CNBC advertisers (M)