Can you explain what makes Falcon9 / Starship special (or needed) to launch these satellites? China, India, EU, Japan etc. all have the capability to launch satellites. So why is a Falcon9 / Starship a particular requirement?
It's more tempo, less cost, resuable has faster turn around time, so more launch per unit of time. Long March 5 is ~$3000/kg, or ballpark enough to F9/kg, but disposables can't launch every few days.
Has to be the cost. A reusable launch vehicle is such a ridiculously better value proposition that it creates a discrete evolution. Some things just arent feasible to do without them
Reusability. Even if money were not an issue, other nations need to build a new rocket for every launch, and it's extremely hard/impossible to catch up.
Starlink is apparently 65% of all active satellites, it would be very expensive to emulate that without super efficient launching capabilities.
None of those countries (well probably except China) have any significant launch capacity to deploy constellations
Cost, maybe? It is one thing to ship up a valuable satellite (which they all can do). But to ship up 1000s of satellites (and keep doing it in perpetuity, because IIRC they don't have a long lifetime[0]) gets expensive.
0: Looks like 5 years. https://www.space.com/spacex-starlink-satellites.html