It wasn't even feature parity or stability- I was very happy with KiCad and had been using it personally for a couple of years.
But when faced with a situation, where some parts of the product were in Altium, some were made by a contractor in Eagle- introducing the third CAD tool made less sense than just settling on the one which majority of team was familiar with.
Over the weekend I put together a toy project with a few ICs and maybe a dozen passives in KiCad and I was amazed to see how easy everything was. And now with a new release they're probably fixing things I hadn't even been annoyed by yet.
Hopefully having an open codebase means we start seeing some nice autoplacement and autorouting trickli6in from hobbyists and academia, like we've seen in the 3D printer world.