We don't know the reasons why suddenly they are waking up after all these years.
Either they just remember their stash or silently following the market.
But no matter what the reason is, it is still part of the 21M supply of bitcoin.
So we can't say, that will have a big impact in the current market value of btc.
Well, the one reason could just be simple they're trying to get rid of it and want to take the fruit of their patience. They're no different from us as they're also people that want to take profit over all these times.
The intention is that most of them have plenty of wallets and not just one, and they use the other ones and keep a few just for saving as well, and that means they are going to end up making that active when they move it around.
Plus, even though the security of bitcoin is great, it is smarter to end up changing the wallet here and there time to time because that way nobody could hack into your system, otherwise your wallet could be hacked into one way or another, specially ones that move away from legacy address to segwit address makes even more sense to me. This is why I believe that it is not always to sell, sure sometimes it could be for selling but there are many other reasons then selling and that could be the reason.
Good point, there's the possibility that it's not for selling but for those reasons that you've mentioned. But the thing here is, we will never know until we know one or someone comes all of a sudden to be one of those owners and explain what really does with those. Anyway, they've got not obligation in doing so to appear in the public.
The best time for whales to move or cash out there Bitcoin was when it was at its ATH or above 50k. Its not confirm but there are rumors that such wallets are hacked and its hacker who moved Bitcoin to some other wallets. The question is if whale has kept his Bitcoin quite for almost decade and didn't bother to move them during 2017 and 2021 bull run they why he is moving when market is relatively bearish. This question never got answer on such movements.
If it's during this time, that's still a good timeframe as the price is much higher than 2017 but not of course on 2021. These could be just woke up wallets and owners have just remembered they own it. Well, it's really confusing but will still be ending up with the same reason of dumping or just trying to move it from wallet to wallet.