There is no "why" dude. We evolved a complex and large brain. The complexity of it allows for such a high level of consciousness. The why is irrelevant and we already have the evolutionary framework to explain it.
So every organism who has evolved a complex and large brain not only shares our metacognition; but we also have a complete explanation for our level of consciousness.
I was starting to get worried that we didn't have a complete understanding of human consciousness.
LOL, how is the 'why' irrelevant? We give very relevant and very detailed explanations as to why we evolved every physical and social characteristic that modern humans posses - However, the 'why' about human consciousness, is the one thing that is irrelevant? Even if we were to determine human consciousness as a mere by-product of a random algorithmic, natural selection process then the 'why' still wouldn't be irrelevant because only foolish people speak of "the development of large brains" in regards to this topic. We have a larger brain only in relation to body size - but our brains are similar in general structure. "humans are not unique in possessing the neurological substrates that generate consciousness." So while we know that, a person like you, still is too shortsighted to even question as to 'why' animal levels of consciousness aren't even comparable to humans?