I hate to break it to y'all, but resellers are not the center of the Lego universe. Correlation does not equal causation, particularly in the aftermath of a market disruption as large as the one caused by COVID over the last 13-14 months. Just apply Occam's Razer...what is a more likely explanation for the extension of Tree House: (a) it is a wildly popular set and TLG fell so far short of fulfilling its outstanding orders from retailers during the pandemic that it decided to extend it to meet the market demand, or (b) a small group of Lego customers who buy for resale single-handedly bought so many copies of one of the most in-demand sets during the pandemic from Walmart, Amazon, and Target (because LEGO Shop at Home was sold out for months) that Walmart, Amazon, and Target placed restock orders with TLG that were so large that TLG decided to extend the life of the set, which it would have retired had resellers not been buying?
At the end of the day, you realize that we all make money reselling Lego when the sets we choose are popular enough that the demand for them outstrips the available supply? If resellers were the driving force behind the extension of certain sets, where would the demand that drives prices increases come from?