Why?
Compare it to some other fanbases. With music, printing a super pricy limited edition of an album with extra non-music content is a normal decision. With sneakers, that's like the entire market. With comic books limited edition posters and figures are commonplace.
So many fandoms have outlets for the rich megafans that the average fan can just ignore without any real issue. Why is it disrespecting the customer? I can understand disliking the side sets having chase cards that are necessary for some formats, and could see those as disrespecting the customer, but not these.
If it was real very rare cards, there would be upset but they could have made it work.
If it was non-cardlike collectibles, it would have been fine.
But to sell non-legal cards at such a high price is so much the opposite of the community celebration they were pushing for overall.
And the last time they sold something like this, it was the entire set and it wasn't expensive. Even if that was a long time ago.
And wizards constantly pretends that all their pieces of cardboard have similar value, so it's extra obnoxious whenever they price something like this. But this one in particular is an order of magnitude worse even if we forget for a second they aren't legal cards.
And various ways of playing the game are actively dying because it's so hard to get cards like this, which just adds salt.
What decision are you claiming people were outraged?
Because the actual reason people where outraged is the very existence of the magic 30th edition in the first place. It is one of the clearest and starkest examples of a company disrespecting it's customer, ever.