I always find it odd when a director -- whose career seems to have been chugging along quite amiably -- just
vanishes for no discernable reason.

This thread idea occurred to me watching the 2014 movie
The Angriest Man In Brooklyn this morning, an alternately tasteless and mawkish mess directed by...Phil Alden Robinson?

Yes, the same man who gave us the sublime tearjerker
Field Of Dreams and highly entertaining caper comedy
Sneakers, then didn't make another theatrical feature for TEN YEARS (2002's bland Tom Clancy flick
The Sum Of All Fears) before vanishing for another dozen years before making this lousy time-waster. Back in the early 90s I always thought that Robinson would have been one of those guys turning out a very good or even great movie every few years, but he just seemed to give up, aside from the occasional screenwriting or TV directing gig.
Also coming to mind is Jonathan Mostow, who hit the jackpot right out of the gate with the terrific thriller
Breakdown, followed that with the terse submarine movie
U-571, and did an admirable job in the unenviable position of replacing James Cameron in the exciting
Terminator 3: Rise Of The Machines, but since then has made all of two movies, the second of which was a straight-to-Redbox clunker starring Sam Worthington.
Anyone else...?