The participant numbers are really low I think.
It always amazes me how on a poker client the operates worldwide even I as a player who hasn't really been active ( and only plays OMAHA games there) late still recognize 12 of the 20 people on the leaderboard.
Shows how small the player base on this site really is.

The population is super small, and super consistent I haven't played in like 5 years and still recognize most of the names.
A small, weak pool isn't necessarily a bad thing though...
Any information if there are any overlays in these tournaments?
The completed tournaments are up on the client for at least the next day, so you could have easily found this information out on your own, or looked at the previous couple of posts where SWC stated the prize pool and gtds from the completed tournaments. Most of the tournaments have exceeded the gtd's, a few of the smaller late night ones haven't.
LOL, why so defensive?
You said it yourself, the completed tournaments are only about 24h hours visible, so I wondered about the previous ones.
So sorry I didn't check the past posts about who won the tournaments, my bad.

I doubt that you recognize most of the players names if you haven't played for 5 years, unless you are in the chat all the time without playing ( popular thing on swc ).
There are plenty of new accounts under those names with low krill level. Also some old players with new accounts, like BigRanch for example.