There are several points that suggest different thoughts.
The first one. These transactions are made automatically. At the same time, the machine has not been controlled for a long time or it has not been controlled.
Where are such conclusions from?
1. The funds haven’t gone any further.
2. If someone got access (remembered, picked up, restored) to a private wallet. That would have transferred the entire balance, and not the first initial transaction!
3. The altos BCH etc., would be moved!
Two options come out of this.
1. There is some kind of script that runs from time to time and transfers funds from wallets that he knows to new ones, while he remembers new addresses and amounts. In this case, the amounts may be different and time intervals between transfers too.
Option 2. This is someone picking up transaction signatures. Created a large number of transactions with large amounts on the basis of current blockchain data, once upon a time, and a subset of these signature transactions. Again, this is some kind of machine. And no one controls, otherwise the altos would have been translated.