I had a 2004 WRX. It was an awesome car and I used it pretty hard. I put 85,000km on it, and in that time the only thing it needed was oil changes, and a spoiler mounted LED brakelight module under warranty. And the warranty experience was wonderful.
Conversely, a friend of mine bought a used Saabaru 9-2X turbo. Basically a WRX. He did a few lights mods, I think an up-pipe and a chip tune from one of the top tuners, I think Cobb. He was religious about maintenance. He used it for a few trackdays. After a handful, he suffered complete engine failure. All the bottom end bearings disintegrated, took out the cam bearings, turbo, etc. We have no idea why. He put a new engine in it and sold the car.
While some may think trackdays are "abuse", they really aren't. Or, they shouldn't be. Properly maintained, they're nothing that the cars aren't tested for by the OEM.
We don't know the root cause, but I chalk it up to it must have been something the previous owner did.