but I will show you why there's a 4-year cycle and how it's related to the 21 million Bitcoin limit
With respect (and I mean it) this post doesn't actually show why there's a 4 year cycle (the first part), i.e. why Satoshi chose 4 years and not say 2 or 5. What it does show is how the 4 year cycle with 10 minute block times is related to the 21 million limit (the second part).