You made your points clear enough. Unfortunately, making them clear doesn't make them right.
Saying that because he was in control of his computer, so therefore he was both aware and in control of his browser cache, and every single file within the cache, is a stretch. That would be quite a legal loophole, and one an activist judge might make to skirt the law as written.
You'd also have to include Website cookies in that. Are you aware of and in control of every cookie on your machine?
Saying that because he sought and and was viewing images on his screen, he was therefor in control of the images on his screen is also a stretch, since those images were being streamed from a computer server of which he was not in control. He was no more in control of those images on his screen than you are in control of the images being broadcast from the television studio to your television. But even if he was in control of the images on his screen, he made no action to save those images to a file. No screencap, no save-as, no nothing. He was purely a passive viewer, which doesn't violate the law. His browser saved some files, tho, but he didn't, and he made no effort to copy those files from the cache to another place on his computer.
Most people don't know what the cache is, where it is, or how to access it. Fact is, it's the browser who has dominion control over the cache, not the computer user, unless the computer user takes some affirmative action to take control of the cache, which he did not. You see it differently, and that's fine, but the law disagrees, as the judge ruled. It's not like he's getting off scott-free or anything. He was merely found not guilty of two charges out of a whole bunch of them, accompanied by a recommendation from the judge to the legislators to re-word the law.