T-Mobile transformed from scrappy challenger to share-taker in US wireless. The Sprint merger delivered a trove of mid-band spectrum that let it build the country's leading 5G network years ahead of rivals, converting network advantage into subscriber growth quarter after quarter. Its un-carrier positioning, contract-free plans and bundled perks, reset industry norms. Majority-owned by Deutsche Telekom, T-Mobile added fixed wireless home internet as a second growth engine and shifted from growth story to cash returner.