This one is a real head scratcher. Williams was Crystal Balled to be 100% to UM in late December. The last MSU post regarding Williams was December 11, 2018, prior to that the last post was more than a year ago on March 26, 2018. MSU will have four senior WR's on their 2020 roster (White, Stewart, Chambers, Nelson), and one junior (Nailor) who are in the playing rotation making it difficult for a freshman to see the field. If he's looking for immediate playing time it is understandable that he is looking elsewhere.
I know he received offers from both MSU and UM, and is the highest rated WR recruit per Rivals, yet he is not considered the top WR recruit in the state by either school, Maliq Carr, a 6'5" WR has that distinction.
Most of the talk on the MSU board going back to last summer regarding WR recruiting was focused on in state players Carr (4*), and Devell Washington (3*, 6'4", 215), and out of state legacy recruit Mushin Muhammad (4*). Carr is considered a strong UM lean, Washington a strong MSU lean.
I haven't heard anything negative about this young man, or why he went from a 100% lock to UM to not having interest in them now.
MLK high school is one of the strongest programs within the city of Detroit that produces many D1, Power 5 capable players. Cass Tech being the other. Just outside of Ann Arbor is Belleville and that program has recently been producing a great number of Power 5 talent, and I have noticed that both MSU and UM have both emphasized recruiting in state players from this program.
Good luck.