First, to address your edit about the downvote: up- and down-votes on Meta are often construed as being in favour or against the proposal of the question. Here I expect that the downvotes are from people being against your initial proposition that proofs on the site should be only solved in "obvious" ways. Since for some proofs, using only things are obvious[$1$] would run to half a book, it should be clear why people disagree with a blanket statement.
Second, to answer your question: answers at different levels can give different insights into a problem and how to solve it. There's a lovely book (I think it's Michael Steele's The Cauchy-Schwarz Masterclass) that looks at the Cauchy-Schwarz inequality and provides about $20$ different ways to prove it, and studies the insights that that leads to. Seeing things in new ways can make the difference between "that's all there is here" and "here's an interesting new direction to study". Many of the proofs are not obvious, but they're no less valuable for that.
Your implicit question (and I may be putting words in your mouth) seems to be actually a complaint that you didn't understand the previous answers. If that's true, then a better question from you would be what can I do to improve so I can understand this? You've made a good start -- writing out your own solution is a fantastic idea, and seems to have led to you learning more as well (judging by the comments on your answer). If your next question were why is this notation used in this answer? that would also be an excellent step; it's essentially your question here but rephrased without judgement.
Lastly: proof-writing and -reading are non-trivial skills. Don't expect to understand all but the simplest proofs on a read-through, and do expect to put some work in to follow the ideas in there. They will reward you in the long run.
[$1$] There's also the issue that the longer a proof becomes the harder it is to keep the ideas in mind, so using only elementary ("obvious") language would make the proof harder, not easier to understand.