Are indies piling on because there is so little money to be made else where in gaming, at present?

As someone peripherally involved with certain VR indie communities, I'd say it's simply that indies do what they want, and there are a lot of people who are extremely passionate about VR. As far as money goes, VR users are very hungry for apps right now, so it's a small but vigorous market.

Platform launches are always a good opportunity for niche games and new IPs because early adopters want to justify their purchase and with a limited library are more open to buying games they wouldn't buy otherwise.