Monero isn't fast enough and doesn't support transaction recovery (it also has probabilistic linkage which MobileCoin doesn't due to our use of secure enclaves). We spent almost 18 months building MobileCoin Fog to solve the second problem (https://github.com/mobilecoinfoundation/fog). It's a non-trivial stack of code to allow users to recover strings from servers they don't control without the operators of those servers being able to learn what strings are being recovered.

Don't get me wrong, we stand on the shoulders of giants, but there's a lot of new tech here.