[dredmorbius]

Even without becoming perpetually dominant, many of them exercised a huge amount of control over a large area for a long time. IBM from the 1930s through the 1990s, Microsoft from the 1980s through the 2010s, AT&T from the 1910s through the 1980s, etc.

There are cases to be made for these reigns being useful: AT&T spawned Unix and (in part) TCP/IP and the Internet, IBM spawned much IC development, Microsoft proliferated cheap and standardized x86 CPUs. But each also quashed competition in the form of both other firms and competing technologies: AT&T, despite the role UNIX came to play in packet-switched networks, explicitly rejected them for its own network recognizing that this would undermine its own dedicated-circuit switching. Microsoft's treatment of competitors is legion, but it's IBM we have to thank for the term "FUD".