Borland seemed to be in flux in the year or two prior to the split. Turbo Prolog was hyped and then seemed to disappear (although I'm pretty sure it shipped a version or two), Turbo Pascal was advertised for the then-new Amiga 1000 and never shipped.

It's hard to understate how critical Borland was in the shift from the BASIC era of home computing for many users and inexperienced programmers in the 80s and early 90s.