It's not only about hosting across multiple providers for the sake of diversifying that risk.
It's an unhealthy situation to be fully dependent on 1 single provider. It creates monopolies (instead of diversity and choice) which means less freedom, and/or more corruption and unhealthy conditions for all involved.
No I get the concern. I’m asking how many companies are realistically mitigating that risk, today. Like why is RoJ being called out for it here, when building systems that are tightly tied to various cloud providers is a pretty common thing (and dare I say the risk is even a bit overblown).