Star Trek got a makeover between TMP and TWOK, courtesy of Nick Meyer and Harve Bennett. Meyer, in particular, wanted to depict a more militaristic Starfleet (hence the uniform jackets and the more formal atmosphere) compared with TMP, but that doesn't explain why the culture of Starfleet would have changed so much in-universe. Starfleet of the 2280s appeared to be drastically different than it was only a decade prior, although the reason for the change was never made clear on-screen.
There aren't many books devoted to the intervening years between TMP and TWOK. Christopher's The Darkness Drops Again novella from the Mere Anarchy series covers much of the time period in question--and even includes a reference to the change in culture when one of the characters ponders the uniform change. Of the other books written during this era, do any mention specific events that may have influenced some of the changes we saw on-screen?
--Sran
There aren't many books devoted to the intervening years between TMP and TWOK. Christopher's The Darkness Drops Again novella from the Mere Anarchy series covers much of the time period in question--and even includes a reference to the change in culture when one of the characters ponders the uniform change. Of the other books written during this era, do any mention specific events that may have influenced some of the changes we saw on-screen?
--Sran