Investors saw a good opporunity to make money in baseball cards and moved in buying up whatever they could. Then the manufacturers started to cater to the investors and making product just for them. Eventually it comes back to the collector. The collectors were not interested in the product any more, since it changed from a collector hobby to an investor oriented hobby. And the hobby crashed. Slabbing played some part in it, because investors wanted the grading and protection, but I think it was mostly the investors and manufacturers that killed the hobby.