... because Apple *invented* the global IP protection laws and related treaties, and no other company on Earth has *ever* resorted to throwing lawyers at anything.
As for renaming their product: Apple had to do just that—and did so without a squeak—with their Apple TV product. (The UK's commercial "ITV" television company has been around since the 1950s, so Apple knew well in advance that "iTV" was never going to be an option.)
ProView's creditors clearly saw an opportunity for blackmail here, and they're running with it. As a Chinese company, they have the legal system on their side too. (Not least because the company's creditors are banks. Chinese banks. And therefore have the implicit support of the state.)
You can laugh at Apple—"Ha ha! Look at how the mighty are, er, still spanking the crap out of all their rivals! And creaming off over 50% of the entire mobile phone market's profits! Yeah! Suck it up, Apple!"—or you can raise an eyebrow at the Chinese instead.
Either ProView sold Apple "global" rights, or they didn't. Which was it? And what, exactly, do they think Apple will do if it turns out the rights sold by ProView's Taiwanese arm were done so under false pretences? (Hint: it'll involve lawyers. Lots of them. And Apple have plenty of money. Unlike ProView, which is bankrupt.)
Worst case scenario: Apple could easily rename the iPad as the "[APPLE LOGO]Pad", as they did with their Apple TV, so ProView's creditors would simply lose even more money. Their only option would be to offer a sale of ProView's remaining assets—including their Chinese territory "iPad" name rights—for a song. Furthermore, Apple could also remove all their manufacturing from China. (That's unlikely in the short-term, but wages are rising in China, so it's quite likely in the medium term.)
Apple haven't lost the war. They're just doing a recce.