A clear understanding of the data is the starting point for understanding other aspects whether that is processes, stakeholders, goals, vision, etcetera.
Data is the core of everything.
Processes simply change data from one state to another.
Reality is captured by data.
Stakeholders deal with data even if the data is directly representing reality.
A clear understanding of data results in a clearer understanding of business processes.
A clear understanding of data is the beginning of innovation.