It's just that the invention is so simple/obvious to us that I wonder how they got a patent and no prior art was found.
I'd also like to note that the quid-pro-quo model of patents suggests that, in fact, it shouldn't be enough for the solution to be non-obvious: It should have to be non-obvious even once you have been told such a thing exists. Because if the mere knowledge of the existence of something would be sufficient to render how to do it obvious, the inventor cannot hope to keep its workings secret once it is released, and so we are trading for something that would be worthless anyway.
In other words, for some kinds of trade secrets, perhaps inventors might not even let you know of the existence of their invention, since without legal protection this knowledge would render the competitive advantage it confers worthless - even though before disclosure, skilled practitioners did not think to use it, as it is quite novel and those skilled in the art have not come up with it despite its obvious utility once disclosed.
Thus inventors might secretly enjoy its benefits or fruits. (This is easy enough to imagine; there could be a closely guarded manufacturing process in use right now that the public and other manufactuers do not even knows exists, and is not in the final product. The manufacturer simply makes an end product more cheaply, say. But telling us what the process is would give it away.)
Imagine, for example, that Google uses some kind of trade secret as part of ranking web pages. We don't even know what the process is, let alone how it is done. Naming the process would render it public and unprotected. So, it remains the only search engine that uses it, secretly.
Source code is often the only way for someone to recreate an idea disclosed via software patent without undue experimentation.