IIRC this was not the newest iPhone. It probably was using the basic 4 number password, giving only 10,000 unique passwords. Even if the phone was set to clear itself after 10 failed passwords, they'd only have to create 1,000 virtual phones, a process which could be automated.
Even a 6 number password would be only a million variations and could be solved by brute force methods. A longer alphanumeric password would be problematic.
Made a virtual iPhone by pulling the chips and copying their contents to RAM in a iPhone software modeller somewhere.