People, including Penn State fans and alumni, wondered aloud why PSU retained Paterno so long after it became clear that he was well past his prime and that the program was declining. This was especially so in the early 2000s when PSU had losing seasons 4 out of 5 years. Sandusky last coached in 1999.
Though I have no evidence of this of this other than what came out in the press about the whole sordid affair, my bet is that Spanier et al encouraged Paterno to retire gracefully with much pomp and fanfare, but he was engaged in a death match with Bowden for the most all-.time victories and wouldn't leave gracefully. To protect his record, and yes, his legacy, I think he told Spanier and the PSU Board that he would go public with the Sandusky affair if they ever tried to push him out before he was ready. I'm sure that he, and they, believed that his reputation as the sainted old icon of college football would lead the public to view him as the courageous whistleblower who fought the academic powers at PSU when they refused to impose real punishment on Sandusky when Paterno learned of his misdeeds, reported them "up the chain," and demanded swift action and accountability from them.