Could you be specific about the size of your company and the size of the data you're processing? And could you also be more specific about the business value it created? Are you an investor in the business? Is it your own money on the line?
When the monolith goes down, it's hundreds of thousands, sometimes millions of dollars of revenue lost both during and as a result of an outage.
You really, really don't want a problem with eg internal staff vacation hours to do that.
It sounds like you're describing a monolith that actually contained multiple completely independent applications - which I don't think anyone would disagree with being a good case for splitting.
In most cases I've seen, the decision to split into microservices usually involves a fairly high amount of dependency between different services to achieve a common business goal (hence the concerns about things like referential integrity)