The thing which makes tech companies different from every other is the 'infrastructure' effect of software and the absence of 'geographical' limits on monopolies.
Banks, law firms, audit firms are fundamentally limited by geography. A law firm in New York will find it very hard to service clients in San Francisco without having employees there. Tech firms arent 'boxed' in by these limits, which are preset for most traditional businesses, thereby greatly expands their ability to become monopolies and strangle competition.
The other advantage that tech companies have is the fundamentally additive nature of software. Microsoft made a very good OS few decades back, but its ability to keep releasing a competitive OS builds on the work piled on by decades of engineering. It is simply impossible for a startup to release another version of an OS which can compete with Microsoft Windows.
However, if we were to break up Windows into pieces, it opens up the possiblity for a new startup to innovate on a part of the OS and buy existing pieces from the vendors of each part to ship a new offering.