"They didn't" pretty easy answer. Also the idea that they lost "even though their products were technically superior to Microsoft's offerings" is sorta unsupported and is obviously subjective.
Having used both MS and Borland products during the late 90s and early 2000s, Borland tools were definitely far superior from the standpoint of ease of use, time it takes to develop serious applications etc.
The primary advantage of the Borland's tools apart form itse its ease of use and was its very interesting component architecture which allowed for very easy development of third-party components and so many high quality third-party components were available free or at low cost. While this was happening MS got lost in the bushes trying to get ActiveX, COM etc to be the bridge for component inter-usability but it didn't come close to the ease of development of components in Delphi, CppBuilder etc.
The issue with Borland was the poor quality of management after their founder left. They tried to get into the Application Development Lifecycle space, bought up a lot of companies in that space and increased the cost of their dev tools to the point that it was no longer affordable to smaller dev shops who were their primary customers.
This problem hasn't gone away. Embarcadero still has ridiculous pricing for their products even though now they have a very stripped down IDE which can be used for free till you hit the USD 5000/year revenue limit.
We used both at university, for designing UI and corresponding events Borland's dev studio was easily 10x faster to design if your UI was a bit more complex, especially if you are not very familiar with whole ecosystem.
MS design of their stuff in those years was often... shitty on multiple levels to be polite, ie MFC comes to mind, over-complicated for no good benefit. People jumped to literally anything else if they could, be it Borland for C/C++, Java had much saner object-oriented design model too (which could be compiled to native code with native UI if needed, since their default stuff didn't look the best).
Borland made the best dev tools in their day, but they sorta lost the edge early in the Builder run and other tools became more desirable. At least, that's why I stopped using them.
I don't know about Mac support. I did Apple development during those days as well, but I didn't use Borland tools for that, I used CodeWarrior.
LightSpeed C, later renamed THINK C, had the Mac market sewn up before CodeWarrior. They had an excellent hypertext help built in, before web browsers. They were bought by Symantec, added C++, and then got beat out by Metrowerks.
I think CodeWarrior was just the superior IDE for anything Mac back in the day. I wasn't a mac guy, but I recall it basically being the only option my buddies would consider back then.
Their products were, and still are in many ways tehcnically superior to Microsoft offerings.
Back in the day, Visual C++ 6.0 was when we finally migrated into Microsoft development tools, and I used Borland tools for ages before that, starting with Turbo Basic in 1990.
Additionally to this day, Microsoft doesn't have anything on the C++ front that can compete with C++ Builder for RAD GUI development, MFC is a fossil, while WinUI with C++/WinRT is a bad joke.
People at Microsoft would probably agree. In 1996 they hired Borland's chief engineer Anders Hejlsberg, who designed Turbo Pascal and Delphi at Borland, and C# and Typescript at Microsoft.
Actually it is a bit more nuanced than that, Anders Hejlsberg was so pissed with Borland's management that he finally accepted the occasional invites from ex-Borland people working at Microsoft.
He tells the story in this interview,
"Anders Hejlsberg: A craftsman of computer language"
By the way, he also contributed to J++, that where P/Invoke, events, Windows Forms, properties came from initially (Yes, Delphi also had events and propertiers by then).
Well, he adapted Clascal & Object Pascal from Lisa & Macintosh to the DOS/Windows PC world, and added a couple features from CLOS to turn it into Delphi, and married that with Sun’s C++-syntax bytecode-compiled variant of Objective-C to produce C#.
He certainly deserves credit for what he did, but not what those whose shoulders he stood on did.
Actually to produce J++, followed by a lawsuit, which made cool from MSR become C#, and J# come into existence to ease the porting from J++ code into C#.
Ironically 20 years later, Microsoft is again a Java vendor, and OpenJDK contributor.
Was and still is, I don't really grasp what kind of Stockholm syndrome goes by at WinDev, that they finally had something that could match against C++ Builder (UWP with C++/CX), only to kill it via a mini-riot, replacing it with a development experience akin to doing ATL with Visual C++ 6.0.
If only IDL tooling, and related C++ code generation wasn't frozen in time, just like it first came in Visual Studio almost 30 years ago, besides updating the actual language to MIDL 3.0, that is.
And now while WinUI 3.0 folks tell the story that you can use C++ with WinUI / WinAppSDK, what they don't tell is the castastrophic state of C++/WinRT tooling in Visual Studio, that there are no plans to improve it past C++17, and the only thing happening ot its repo is bug fixes.
Stay away from it as much as possible, and using it with C# and CsWinRT is not much better, as many errors are surfaced as HRESULT exceptions, and you need to actually single step into C++/WinRT code to actually find out the real cause.
