Actually, part of the criteria for getting a patent (at least in the states) is that the invention is non-obvious to those in the trade. So patents kind of are about doing things that are hard.
And you could argue that zooming in on an HTML bounding box would be obvious to an engineer developing web browsers.
As Rob Pike has said about his patents, everything is obvious in retrospect.
In any case, if it's so obvious, where's the prior art? It's not as if web browsers haven't been around for nearly 20 years.
It seems to me that Apple has justification to defend wholesale copying of the myriad of little design decisions that they made that are synergistic. It's clear that they spent a huge amount of effort and cost doing this, and were able to succeed in a way that many had tried previously and failed.
The legal ways that one can defend such synergistic design work is limited. One common way, for better or worse, is to patent some of the individual elements to throw gum in the works of anyone trying to make derivatives of your work.
Web browsers on tiny devices that have the processing power to do a scaled zoom in a reasonable period of time have most certainly not been around for 20 years.
And you could argue that zooming in on an HTML bounding box would be obvious to an engineer developing web browsers.