A recent book review by Ayelet Haimson Lushkov has some very insightful observations on this very topic:
[W]hile we know very little about the middle republic in comparison to
the better documented period after 133 B.C.; what we do know suggests
that the problems of the late republic were built into the system
almost from its foundation. People like Scipio Africanus and
Flamininus stretched the limits of what Roman society was willing to
tolerate, and while they were more or less successfully brought back
to the fold, the difference between them and Sulla, Caesar, or Pompey
was in degree and not in kind.
Very briefly she goes on to offer a possible theoretical explanation:
The system of aristocratic competition
demanded that individuals amass ever-growing personal and political
fortunes, and historical circumstances gave them the opportunities to
transform political clout into a cult of personality.
Much like in some Greek city states, I believe.
Furthermore, if one is looking for (possibly apocryphal) even earlier precursors to the outsized personalities of the late republican warlords, Coriolanus and Spurius Maelius come to mind.