Carageenan is a perfectly servicable gelling agent - put enough in your beer and you get beer jelly. Its a very common food additive used to thicken and give mouthfeel and is what they often use to make low/no fat things feel like they have oils and fats in them. No fat salad dressing being a typical example.
In beer it isn't doing that - in beer its there because in solution it carries an electrical charge, the opposite of the one carried by the proteins polyphenl/protein complexes that are cold break. It makes them come out of solution more readily and stick into bigger chunks.
Use too much - and you get left over charge on the break particles. And anyone who's rubbed a balloon on their head, knows that a lot of particles all with the same charge are going to repel eah other. The repulsive force opposes the gravity force and over-fined beers have break that does not settle compactly. The particles sit up all fuzzy, just like your hair after the balloon. They dont ever settle as well as they could, and they take a very long time to do it.
Use way too much and you start to see the gelling thing happen and instead of particles, you get a light almost fairfloss looking network that as near as I can tell, never settles. I've heavily over fined to see what happens, and after a month in the fridge, a 500ml sample still had only a cm or two of clear wort over a large mass of break material.
The PVPP - probably didn't have a hell of a lot to do with your jelly monster. Carageenan by itself would perhaps have been worse?? but would still have done essentially the same thing.
TB