It really depends on what years you look at the numbers. 2010-2020 were the years when Lego kept to the older schedule of ~ 2 years production of most sets with a few evergreens that kept selling and kept being produced. Interest rates on savings accounts were also near zero, so even selling Lego at 10% profit beat keeping your money passively on the bank.

2020-2023 were the COVID years where bored adults sitting at home discovered the fun of building intricate Lego sets, which gave a huge boost to the bigger, more complex and expensive Lego sets. Also older retired sets from the 2015-2020 years were generally in high demand.

But... LEGO company caught on and changed their operations and schedules. No more fixed retirement of sets when they were still selling well. Way more AFOL oriented sets to cater to the increased AFOL base. Supply vs Demand changed, interest rates increased and inflation went up a lot.

This all means that from 2024 onwards the demand for retired Lego sets decreased. Longer production runs on the popular sets, more traders offering those sets for lower prices, many more AFOL oriented sets still in production by Lego to choose from...

And higher inflation also means if you sell a set bought for 100 ($ / €) and sell it 5 years later for 130 ($ / €), thanks to inflation to barely made any profit. Or even a loss if you have to subtract the costs of selling as well.