I don't see how it isn't obvious which way the causality is swinging. Toxoplasmosis isn't causing this great variety of symptoms, that makes no sense. It's more like people with a great variety of symptoms use cats to cope with life.
The only reason cats look like a gateway pet is because the same dealers sell both cats and dogs - and everything up to venomous tarantulas and constrictor snakes. And you bet they make a better profit off the more dangerous pets, because you need more equipment to use them on a day-to-day basis.
The feds let it happen because eventually all retail chains get a chunk of the sales. Food, enclosures, electronicals, silicone sealants, plastic containers, special furniture, all bought with hard-earned cash that could have chosen otherwise.
Pets are the real matrix.
It's possible that it's a little of column A and a little of column B rather than either/or. People tend to want to "pick one" (and only one) and that's often a poor way to try to sort out what's really going on.