Certainly they have scale advantages, but there’s also diseconomies of scale that can work against them.
Rather the chilling effect - the firms themselves (may be) slow to perceive the next iteration of consumer needs.
Startups on the other hand figure them out - and build a product.
The big fish/spiders, with their larger webs, sense the new upstarts and THEN build those features - and then go back to whatever it was that they were doing. The cycle then repeats.
Never mind that MS had pulled something similar vs Novell some years prior, by bundling a client with Windows and then marketing their Exchange server as a drop in replacement for Novell's Netware. Just set up a NT box in the server room, configure the PCs, and phase out Netware.
when it's your startup it's 100%. But they don't need to score perfectly always. They can raise your costs by 100 fold if they want, and if they fail, so what, they try another thing. Time and time again and still have tens of billions in bank. The startup has 4-5 months of salaries, if lucky.