It's not that. Like most niche AWS services, this was likely the "pet project" of a major AWS customer that wanted something like this as part of a major business agreement [0]. And then after building it for that customer, AWS also expanded offering it to anyone else who wants to use it.

0: https://blog.maxar.com/earth-intelligence/2018/sending-data-... (posted the same day Ground Station was launched in 2018)