What issue led to civil wars in the roman republic?

First, I will assume that you mean civil wars - - Marius vs. Sulla; Caesar vs. Pompey; Octavian/Agrippa vs. Antony/Cleopatra. If we go into greater detail, there were even more. One observation is that many of these civil wars happened during the end of the republic (even if they did not know it was the end of the republic). From this perspective, something had to be done to restore peace and stability. This paved the way for Octavian to come into power. One can even make an argument that it was these wars, in part, that made room for Octavian. That said, he ushered in the peace of Rome (pax romana). The people loved this peace and quite frankly needed it. The bloody civil wars ravaged the Roman people. A quick glance at Vergil's work show the ethos of civil war and the hope for peace.

Eventually, Octavian (later to be called Augustus) introduced a new form of government - the empire. After Augustus, there would be emperors. Also from a cultural point of view, Augustus' reign would produce some of the most important works in the Latin language - Vergil, Horace and Ovid, to name a few. However, it must also be stated that civil wars would continue. In 69 AD, there was no less than four rival emperors fighting it out.

hope I helped