No idea. Contracts I am seeing nowadays all seems to be all about web apps and mobile apps are afterthougts. From about 2012 - 2016 it was all about mobile first strategy.
I doubt it's related at all. A client probably wouldn't specifically ask for a "React Native" app.
I would think this trend has more to due with app marketplace saturation.
True but the consulting firm/company might find it cheaper and easier to find 'react native' devs than a swift programmer.