It sounds like they were in a place that a lot of companies are in where they don't have a single pane of glass for observability. One of if not the main benefit I've gotten out of Datadog is having everything in Datadog so that it's all connected and I can easily jump from a trace to logs for instance.
One of the terrible mistakes I see companies make with this tooling is fragmenting like this. Everyone has their own personal preference for tool and ultimately the collective experience is significantly worse than the sum of its parts.