Carrier-level telco is labor intensive.

You're building new cell towers, managing countless failed backhual links (thanks to fiber's natural enemy, the backhoe), working with whatever obscure bugs your MVNOs have managed to uncover, certifying new cell phone designs, and still working on upgrading everything to 5G while simultaneously planning for 6G (keeping in mind that the 5G network architecture looks radically different than the LTE architecture). Much of that work is necessarily physically distributed across the entire country.

Not to mention dealing with end-user sales and support, which unfortunately often needs physical stores.

I'm not going to say whether 100k is too many, but there's a lot more involved here than just maintenance and monitoring - especially if you want your network capacity to keep up with growing demand.