Each of those companies had a profitable near monopoly, and were heavily vertically integrated.

Xerox PARC is a bit of an outlier, they didn't commercialize much of the things we remember them for. But Bell labs and IBM Research fed Bell and IBM lots of commercially viable stuff.

The reformed ATT is dominant in its industry, but one of several, and its industry is no longer all forms of real time communication. And afaik, they don't make any equipment anymore, etc.

There are not so many vertically integrated companies anymore. The market values the parts moee than the whole, so spinning out manufacturing or logistics or etc is a popular thing.