If Monk had a mental illness and/or used drugs it was kept pretty much a secret. I hope and suspect the incident culminating in his wandering the airport grounds was an isolated incident.
'Course, Horrywood's gotta make money....And, everything has to relate to today's crowd, the now generation. Jazz music isn't currently popular, but dope and "sensationalism" is. Personally I think Monk's music, the musicians and their interactions and families would be sensational enough for a flick.