Google and Sprint have a very interesting past when it comes to telecom, which is why the announcement about Google Fi and 5G via Sprint is really interesting. Looking back at history, Google and Sprint became friendlier when GoogleVoice numbers were first made usable as the primary mobile number on Sprint's wireless network. That ended last year but it was something that was really useful so its no surprise that Google and Sprint and teaming up again.
When you look at Fi adding 5G radios to the next generation of Pixels phones and then other Androids is a smart move. Already Fi is tightly woven into T-Mobile, especially for global roaming, but having Sprint's flavor of 5G also means tighter integration with Qualcomm's chips and engineering support from Nokia and Ericsson.
This move is more than just about Fi, as so much of it future proofs Google and access to its most important asset. You, the customer.