Around 1996-1997 is when you had early signs of things going awry, when Borland tried to rebrand as an "enterprise middleware" company focused on what they called a three-tier architecture, with COM/CORBA clients talking to server middleware and databases. They bought a CORBA company called Visigenic at a time when CORBA was arguably already old hat, while also betting on COM and Microsoft Transaction Server. They were trying to get into the same enterprise space as Microsoft and Oracle, but then the web arrived and everything started moving away from desktop apps. I don't think they had the enterprise DNA as an organization, and renaming Borland to Inprise couldn't magically fix that.
It arguably started long before then. Borland had a messy history of spreading themselves too thin, trying to do too much, constantly betting on the wrong horse, and ultimately never really finding their feet. Buying Ashton-Taste to buy the already-antique dBASE strained the company, and they went off on weird wild goose chases like Borland Office when WordPerfect was already dying, and they missed the web revolution with the whole Inprise thing. They might have survived if they shed some weight and laser-focused on development tools like Delphi, but a lot of the company seemed to have been pulling in multiple directions.