(wikipedia)

The Turbo Pascal compiler was based on the Blue Label Pascal compiler originally produced for the NasSys cassette-based operating system of the Nascom microcomputer in 1981 by Anders Hejlsberg. Borland licensed Hejlsberg's "PolyPascal" compiler core (Poly Data was the name of Hejlsberg's company in Denmark), and added the user interface and editor. Anders Hejlsberg joined the company as an employee and was the architect for all versions of the Turbo Pascal compiler and the first three versions of Borland Delphi.[2]

Martin Odersky of Java generics (Pizza compiler) and Scala fame, worked on Modula-2 compiler at Borland.

Part of it is that by 1986, CP/M was dead for new development of anything, and Modula-2 was also on fumes.

It would have been business malpractice to spend money on CP/M products at that point.

Depends on the country. In the UK, the Amstrad 8256 and 8512 were very popular, and they were only launched in 1985. They were much cheaper than PCs of the time, and came with wordprocessor package and CP/M 3.0. We had about 25 of them in our lab, including one floating at 4000V in a perspex cage, used to control a C14 accelerator.

From memory, I used TP and them TM2 on CP/M to run an automated thermoluminescence rig, then FTL Modula 2. I wasn't very professional at the time, but then no-one was - most of us were working in isolation. Speaking from that perspective, I was not very impressed with Modula 2. The issue was not with the fundamentals, but the way that it was case sensitive and forced you to use caps for all the keywords, so that it was really annoying to type. As a lesser issue, the names used for type conversions between numeric types seemed to have no rationale, so they were easy to forget. I don't remember exceptions in TM2, and they would not have been part of the standard language. They appear to have come in with Modula-2+.

They were very nice machines. I wrote my first useful programs on these using Mallard Basic to help with my school work. The word processor was really powerful too. I would have turned in my schoolwork using this too but that was unheard of at the time.

There were a couple of Modula-2 vendors for MS-DOS and Amiga. It was TP on MS-DOS, Object Pascal on Mac OS and stuff like BASIC compilers on the Amiga side that made them lose market share.

So? TP real success came with the port to DOS, but TM2 couldn't have been much harder to port.

They probably reused a lot of ideas in Turbo Pascal 4.0. It had units which were very similar to Modula 2 modules, except that interface and implementation were in a single file.

Most of those ideas come from USCD Pascal, and the later Object Pascal introduced in Turbo Pascal 5.5 came from Apple's Object Pascal, which was derived from Clascal and developed in collaboration with Wirth.

Probably, but there were many other language differences in Modula-2 that made it a better language. I suspect the real reason was the usual one: inertia. A lot more people knew Pascal and thus more bought TP than TM2. <something something about technical merit and popularity contests>

The PC Turbo Pascal compiler was written in assembly by Anders Hejlsberg, of C# and Typescript fame.

Personally, I always have the opposite feeling; C# and Typescript was written by Anders Hejlsberg of Turbo Pascal and Delphi fame.

Second vote for me. While C# may have the greater 'head count' in usage now. TP and Delphi were ground breaking, revolutionary products IMHO.

Voted with delight because that’s precisely the way I feel. But I’m trying to make it easy for HN’s young whippersnappers to relate ;)

I can't vote but supporting as third :-).

This is the history as I remember it too. IIRC Topspeed C was an excellent compiler.