This implicates a few things - (1) people win the lottery every day and (2) it's highly unlikely that the best techniques are publicly known.
Perhaps there's something that requires $1,000,000 in investment to yield a 1:100 chance of finding a particular targeted wallet using some clever shortcuts.
The other explanation is very implausible: a human sits on wallets without splitting up the funds or derisking exposure, has wallets with a billion dollars sitting it in.
Now I only have a few million, but even I have something like 6 brokerages and 12 banks. Even when I was a btc holder, I didn't keep over $100k in a single wallet.
The snatching theory requires no new revolutionary math, no substantial breakthroughs, just some clever people with a lot of resources and a goal.
Either explanation is speculative. I think the "lucky researchers at some University" theory is more likely then the "let's wait 14 years until this $1,000 becomes $1,000,000,000."
Especially because (1) we're not exactly at some high water mark and (2) if this was just a person with a wallet trying to do something like pay for life's uncertainties, you can do basically 100% of that with like 4btc.
However if you successfully snatched the wallet, you're on a clock before someone else gets it. This is exactly the kind of movement you'd be doing
Also if some old bitcoiner comes out and says "hey that was me", we're still up in the air. If I had snatched a billion dollar wallet, the first thing I'd do is payoff an old btc'er to claim its there's to prevent market panic.