It would appear that there's a number of factors.
I do think that by the mid 80s, many, certainly pop/rock sound engineers/producers, were aiming for a sound with more treble. Less "warm", if you will than in the 60s and 70s.
To me, many recordings from this era sound overly bright, and need a fair bit of bass, midbass boost to sound anywhere near right to me.
Another possibility is that valve amps where more prevalent back then, so a bright mix gets that warmth back via the playback equipment. (As is also often the case with vinyl, via the cartridge, preamp etc.)
A couple of examples off the top of my head are ones I posted in a thread about "Yacht Rock"
Post in thread 'Got Yacht Rock?'
https://www.audiosciencereview.com/forum/index.php?threads/got-yacht-rock.71002/post-2578451
A bright sound. Went with the questionable clothes...
Jan Hammer... Miami Vice etc!
Have to say that I prefer this type of 80s bright stuff through my valve amp, but EQ definitely works too.