Sprint had outdated technology w.r.t their infrastructure and cell towers, so an outside acquirer didn’t make as much sense. It needed an existing player with more advanced infrastructure to take on the customer base, or a large investment in upgrading it’s own infrastructure.
Pretty much this. Sprint bet the farm several times on ultimately dead-end tech (CDMA, WiMAX) and were too focused on other things to get ahead of technical evolution. They ended up saddled with debt by the end of it, which hampered any ability to actually upgrade their networks (another poster already pointed out the technical issues with running LTE without UMTS). By the time of the merger, the only things of any value they had was the spectrum and customer base to be moved over.
An external acquirer would almost have to build from scratch after absorbing all the legacy costs and run the risk of inheriting Sprint's bad business decision culture or spending an enormous sum building out a new team. Of course, they'd still have to support the old and new setups at the same time for awhile as the new stuff was built out. The ROI would have been decades at best.
With a merger with another telecom, people can be migrated over already existing infrastructure (with some upgrades to deal with new traffic) and have sprint's old spectrum slowly merged into the existing infra.
I'm oversimplifying of course, but one gets the idea.
