Diocletian made a unique move in the history of leadership. What brought him to the realization a division was necessary? Lack of strong leadership internally meant chaos reigned and money became worthless.
Invasion by other countries drained the treasury, as war continued until lost land was regained.
Travel on roads by merchants for trade was no longer safe.
The empire was too large to be ruled by one person.
Due to high inflation, most trade was done by bartering.