Why? Because China is a huge market and because it is not a friendly market. And because Maxthon is probably the most used browser in China after IE. And most of all, Google did what Yahoo! & Microsoft didn't, buy a stake in Maxthon. That's what Tech Crunch is reporting.
Maxthon is a great browser, although I do admit ever since I've installed ie7pro, my Maxthon usage has dropped in favor of IE. Yet Maxthon packs a lot , giving you a large array of features at half the memory footprint of Firefox.