COM was a pretty great tech at the time - nasty to program with but in terms of comprehensiveness of adoption, powerful cross-language interop and component marketplaces, the 90s were the place to be. Microsoft led by example and so lots of apps did expose their internals via COM objects.

For better or worse the shift to cross-platform development killed that all stuff off. The closest equivalent is now the JVM, but it requires everything to share a runtime whereas COM was much less imposing. Also the higher level nature of JVM bytecode makes it less attractive to build commercial components in it, whereas OCX controls were a working market of software components.