Based on the physical evidence, I believe that inscription actually has no bearing at all on who built it, when it was built, or why it was built. It simply means there was an entity called "Khufu" that people wrote about. Doesn't even mean it was a person.
In fact, I am actually uncomfortable with the debate about the authenticity of that particular cartouche because it erroneously lends a credibility to that painting that it simply does not deserve. Truth is, it doesn't matter whether Vyse forged anything on that cartouche because such a vague reference to "Khufu" actually does not say that a man named "Khufu" built the thing at all, let alone in the 4th Dynasty when they did not have the tools or means to build it, or that it was at all intended to be a tomb.