[Someone]

Why do you think latencies would be low?

https://en.wikipedia.org/wiki/High-frequency_trading#History:

“At the turn of the 21st century, HFT trades had an execution time of several seconds, whereas by 2010 this had decreased to milli- and even microseconds”

At the speed of light, a millisecond gives you 300 km, so even assuming zero switching and processing time, you’d have to put your data center in an orbit lower than 150km. That’s less than halve the height at which Starlink operates.

I don’t know how long a satellite lasts without maneuvering in space at that height, but suspect it will require lots of fuel to increase the orbit, or will be problematic to fill and backup such a data center before it burns up on reentry.

Also, of course, a data center in such an orbit almost never will be directly overhead. At times it will be at the other side of the planet, adding over 100ms.