I doubt it was at once, if that figure is 100% correct to begin with. Many months into some years is more likely. But "wiring" bunches of money to China without taking extraordinary measures, is really asking for trouble. It may be what started the problem.
And no, it's almost impossible to believe this developed under Trump, even if it turns out he's worse in this regard. Too much, too soon imo. Especially that 300-whatever figure. Without proper care, if they'd managed to get even half that money to China before being detected I'd be surprised. It's very possible they'd been under surveillance before Trump was even nominated.
But I guess we'll find out.