I do not think that Reality XP was literally Shut Down, but instead, chose to not pursue adding their “Licensed Garmin Trainer Solution” to MSFS, mainly for technical reason with MSFS and the inability to implement the methods they felt were necessary to meet their technical standards, in the way that they were able to in other simulators.
The loss of Reality XP (and its developer) in MSFS 2020 was MSFS’s loss, but turned out to be X-Plane’s Gain.