i've thought about this, but if it's a hardware wallet they would have to physically break into your house or something on anecdotal evidence. that's pretty dystopian.

one wallet could represent one million people and one person can represent a million wallets.

if we assume this is one person with all of the funds under their power then they would have a lot of liquidity issues if they wanted to sell all at once. for big traders it's a process of unrolling the line, which means unloading in chunks or gradually so that they don't rip the market down and get filled at terrible prices. for instance he could put all the funds on one exchange and hit the bid for all of it, but it would push the market down instantly to a lower and lower price, he may get filled $100 for his last btc; not a very elegant exit. big traders massage the market into their traps because they desperately need liquidity. big traders are working as many exchanges as they can at the same time for that exact reason. hell MM don't care what the price is.

they have very little incentive to hit the market with everything. the only situations i can think of is a fat finger or if bitcoin is fundamentally broken and no longer serves it's purpose.