Why and why now? Someone posted a clip of Steam Deck running SteamVR[1] - Could this be the reason, that Facebook is compelled that they need mobile SteamVR to run on Facebook hardware, as a leverage or an insurance?
It's pointless for Facebook to have their hardware used if it's not tied to their accounts and ecosystem. More likely, the Oculus Go is obsoleted enough by the Quest 2, that they decided they didn't care.
1: https://twitter.com/yunayuna64/status/1441288908659048453