Building on the other comments here, SpaceX has more knowledge and certainty about recent and upcoming launch economics than other satellite providers, which opened up the possibility of a system like Starlink. Starlink is capable of such higher bandwidth and lower latency due to its lower orbit. Each satellite has a fixed amount of bandwidth capacity, and the area it covers is based on how high it is (how much of the Earth it can see at one time). High orbits mean they cover more area and spread that bandwidth out between more customers, low orbits mean less coverage area per satellite (so you need lots of satellites for global coverage) but more bandwidth per customer in that area.