Why is AWS enabling managed Grafana when they have Quicksight?
Maybe enough people love Grafana that it's a good business decision to make money from it?
yeah this, there's money to be made from "let us run your existing grafana" that isn't there to be made from "why not port the whole thing to a different platform".
The first is less infra to manage because AWS does it for you. The second is much bigger project and therefore a harder sell.