Most older cell towers could only cover small 3km client service areas, and would max out at a few thousand users. However, as the broadcast power dropped more cells could be installed in busy city centers. The base-stations themselves were often direct fiber service for lightning strike isolation.

Modern beam forming networks with G5 and newer... greatly increased the bandwidth, mobile battery life, and total user capacity of the smaller broadcast cell areas.

Starlink offers budget telecom connectivity in areas that didn't support normal telecom infrastructure, and these sparsely populated wide areas make sense for a LEO uplink.

The terrestrial telecom infrastructure is a different business, and firms have embedded themselves politically for over a century. Starlink would need to risk a great deal for locations to get the density necessary to disrupt the entrenched market, and ultimately could just become another telecom merger in the process.

Iridium tried to enter consumer markets with emergency and industrial coverage options. However, at its core it is an antiquated technology requiring large popcan sized circularly polarized antenna modules, scheduled >5W RF message uplinks, and $3.15/kB service rates.

Part of Starlink success was correlated with how bad Iridium serviced customers. In general, buying a laggard is an opportunity, but I personally don't think Iridium can escape its entrenched business model. They are 20 years too late, burned consumer goodwill, and have competitors already in profit mode. =3