Not fully letting your infra depend on a "smaller" cloud provider (who is notorious for shutting down offerings) should certainly also be pointed out as a risk.
Monoculture in browsers and search engines means they can exploit their dominant monopoly position to be abusive to the community.
GCP not being the biggest means there's not enough momentum to satiate googles avarice, which leads to ambivalence towards customers who have critical infrastructure on their systems.