The PS2 was backwards compatible with all PS1 games. The original phat PS3 was backwards compatible with all PS2 and PS1 games.
So not true to say Sony had no interest in it before - Sony were doing backwards compatibility before Microsoft. And this was true backwards compatibility where you could literally put any disc from a supported console in and play it, not have to wait for it to be added to a list of backwards compatible supported games.
The PS2 was backwards compatible with all PS1 games. The original phat PS3 was backwards compatible with all PS2 and PS1 games.
So not true to say Sony had no interest in it before - Sony were doing backwards compatibility before Microsoft. And this was true backwards compatibility where you could literally put any disc from a supported console in and play it, not have to wait for it to be added to a list of backwards compatible supported games.