Yeah, nobody can know for sure what is going on, we can only speculate. My most likely scenario is they were advised by their custodians to split coins in many addresses because they were being tracked by the market and hence, they needed to increase privacy. But its also possible that the decline in whale address is reflecting of rebalancing (this would also explain why the price of BTC stagnated)
If the former is happening, then relying on on-chain indicators will prove more and more tricky because the big money will use people's expectations to fool them, as the funds learn what is being monitored, it becames really cheap to create false signals. If its the latter, then its a sign were are in for a slow grind bull market in BTC as the days of maniacal buying and hodling from retail determining the price are over