Addresses and money like this move all the time, sometimes people are looking around for them and see them. Many times they do not.
The OP seems to be digging into and poking around old addresses for some reason. I think everyone who gets into BTC does that at some point in time.

Old addresses with a lot of funds are not that big a deal. If they have 1 like that they probably have more.

Not something to worry about the trading volume of BTC is on the order of 1.5 million coins a day. Having a few thousand more dumped into it is not something to worry about.

-Dave