It's not an excuse, but this might explain why Richard III mightve been one English monarch who was erased by history by later historians, playwrights, authors, royal chroniclers and subsequent Tudor, Stuart dynasties--part of it had to do with his alleged involvement in the kidnapping, disappearance and likely murders of his two cousins held as hostages in the Tower of London, The Princes in the Tower. Some also accused him of poisoning his brother, Edward IV of York.
Many at the time before his death at Bosworth Field in 1485 (last English/British monarch to die on field of battle), and especially afterwards, blamed Richard III for murdering those princes because they were a threat to his short-and-probable long term reign and the subsequent Tudor dynasty who replaced Yorkist monarchy claims of legitimacy were on shaky grounds even after defeating Richard so they did a posthumous, post-moterm character assassination blaming all sorts of suspicious activities and malicous deeds upon him (whether he was guilty or not).
It was a very well-concocted, constructed story that was widely-believed and accepted for centuries until maybe the mid-late 19th century when scholars and historians began critically analyzing and reviewing some of original primary/secondary source material where the crimes attributed to Richard posthumously were leveled and found quite a few of the accusations lacked merit or had flaws in them.