We are not dealing with Woodward & Bernstein here, but of course their claim to fame took about 9 months after their reporting started before the coverup blew.
Far more important scandals than this covered by news organizations with much greater resources have experienced delays in being disclosed. A credible publication presumably requires credible sources before anything can be reliably reported.
It is not as if Bouchette is covering a government organization and can file an open records request or a large organization containing numerous potential whistleblowers with the motivation to blow something up (Woodward & Bernstein's Deep Throat was a senior FBI official who was pissed off he did not get the Director job after Hoover died).
As far as running it down, you are dealing with a very small group of potential sources (players, coaches, front office personnel), all of whom had an incentive to keep the leaky boat afloat during the season. The cover story of AB rehabbing a knee injury in week 17 held until the Steelers were eliminated, at which point Dulac and Bouchette had the sources to report the day after the season ended what was going on with AB in the run up to the Bengals game.
https://www.post-gazette.com/sports/...s/201812310108
Probably the same sources who told Bouchette about the week 17 cluster told him after the end of the season what actually was going on during training camp and after the Chiefs game now that those sources are seriously pissed off at AB and there is no longer the same interest in underplaying any problems or any drive to the playoffs to avoid disrupting.
Everything is now being viewed from the perspective of a season that crashed and burned. If the Steelers had won the Super Bowl AB allegedly leaving the team after the Chiefs game probably would be portrayed as showing his commitment to winning, as was the case when it came out that Joe Greene threatened to leave the Steelers in late November 1974 after a bitter loss before that first Super Bowl season turned around.