they started it, yes. which included all their sub-pools.
foundry joined in about a week later iirc.
mara just stopped because they didn't fancy losing 3.125 Bitcoin in an orphaned block to get an extra $14 for mining a pile of spam.
Positive side effect of destroying illusions: The pool I'm mining to becomes visible in the pie chart.
Do you have more info about the connection of AntPool and friends?