Hasbro is also less likely to send C&Ds over shit than Nintendo is. These days people are becoming terrified of doing any fan projects, Nintendo has really picked up the pace on that since the new guy took over when Iwata died, but Nintendo once sent a legal threat to a website that simply discussed the EXISTENCE of bootleg Pokemon toys. Meanwhile Hasbro bent over and took it when hundreds of Chinese companies started making unofficial Transformers toys- in fact the only times Hasbro has been known to go after any Pony shit are the plush makers who charged big bucks for unofficial merch, and dumb bitch Kayla-Na selling pony porn, even then they limited to US individuals making hefty profit, and still not even an actual lawsuit or fine, just a C&D letter.
Pokemon designs also vary and require knowing how to draw humans- as some people want the trainers/Team Rocket instead of the animals- while >>91305 is right, most every character uses one simple body.
I also think many Pokemon fans were content to buy the official games & merch too, while the pony porn fans never watched the show or bought the toys, so their whole fandom was built on unofficial smut.