Why should the circulating supply be less than that and where do you see a dump? Several millions? Please enlighten me.
Question is : why don't you worry about it ?
Here is the answer, you have sell most of them : (and you took the right decision)
Total Sent (ONION) Total Received (ONION) Balance (ONION)
563,810.76662691 629,065.34027882 65,254.57365191
Some are smart, as you did, but many will loose everything.
Learn to read the block explorer.
The only thing this says is that this specific address received more ONIONs than it sent out.
In fact I know that the user you are attacking here received less than 65k via the airdrop. Which means - for you - that he bought a significant amount of ONIONs and he's still holding on to them.