2 650k BTC - 2 900k BTC this is only 10% range (or 1.4% of bitcoin supply). Its not that much of fluctuation to draw far-reaching conclusions.
2 900k BTC out of 18 430K BTC = 15,74%
2 650k BTC out of 18 430K BTC = 14,37%
Not a big change.
But if I had to estimate what is a reason i would go with:
1- bitcoin is boring, stable at 9000 for 2,5 months, whoever wanted to buy/sell at these levels already did that. And we can observe that by declining volume.
2- Futures and options are getting more and more popular.
And that's all. All other aspects are negligible in my opinion.
Edit:
https://studio.glassnode.com/metrics?a=BTC&m=distribution.BalanceExchangesAllZomming out - this is only a small correction