That is definitely suspicious but you or me and no one can prove it so we should just let it go :/
You also have to consider that the people with these ridiculous amounts of crypto likely don't want their identity known. That includes both their real life identity and online. Think of how many click bait articles would be written the second anyone confirmed who they were. If they want to gamble big, it make perfect sense for them to just hop from new account to new account and it makes perfect sense for stake to allow them to do that. I wouldn't be surprised if the AABB account owner is done with that account already.
Per stake TOS , this point doesnt apply
https://stake.com/policies/anti-money-laundering"Withdrawal Threshold KYC. Additionally, and independently, every account, wherever or with whomever associated, will be suspended until adequate KYC diligence occurs once that account reaches a withdrawal threshold dependent on the accounts risk characterisation over the life of the account."
Now how much of that stake is implementing , is another question
But, per that rule, stake is NOT anonymous friendly casino anymore.