There is a school of thought (with some validity, though I think it lacks nuance) that points out that the early Roman Empire, the Principate of Augustus until the Dominate of Diocletian, tried to empower the Senate. The Senate had its set of provinces, the emperor his. The cursus honorum was still used to track and groom administrators and leaders and the senate's support (balanced against the army and the people of the city of Rome generally) still legitimized the emperor. But over time, goes this line of thinking, senatorial attention and interest fell away somewhat from administrative and managerial responsibilities and turned more into a social/politicking club, and the emperor "naturally" picked up the slack.

There is an element of bias to this, and it often reveals a political preference of the author, but it's not without some merit.

I believe the claim is that the Roman emperors came about because the Roman senate became so mired in infighting that it was incapable of governing. I'm not a historian, but from what I understand, there is at least an element of truth in the claim.

For a detailed version of this argument, I recommend Edward J. Watts' Mortal Republic: https://www.goodreads.com/book/show/39088591-mortal-republic

I was being a bit glib, and others have expanded better than I can on the theory (plus Roman politics is complicated) but here's an example of the theory: https://www.history.com/news/rome-republic-augustus-dictator