Hello, team has been discussing rollups from much earlier. In fact, they had early design discussions back in 2018. 

But in order to implement rollups they needed to mature the Cartesi Machine. In 2020 they were very focused on that, which led team to Descartes v1. Then they had the late 2020 PoS sprint.

In the last couple of months team finally started to bring much more attention to the rollups architecture and implementation.