There are several recent books, The Byzantine Republic by Kaldellis, most notably, that argue that civil wars are the Roman (and so, not specifically Byzantine) system working as designed.

Basically, the Roman succession system is almost unique to the world (with the exception of China, and arguably the longevity of both Rome and China is due to this system) in that it is a dynastic system which tolerates dynastic replacement without a replacement of state identity.

With this being the case, civil wars simply become "military elections." Because keep in mind, a civil war does not inherently have to be interfactional, it can also be separatist, i.e. regions could be fighing for independence. However, that is rarely the case with Roman/Byzantine civil wars. More often than not, they're interfactional wars where the goal is to take over the entirety of the state, not separate from it.

There was an excellent book on the politics of the Zulu Empire (that I forget, maybe ask /u/commustar) that said roughly the same thing. By all accounts, the Zulu Empire should not have held together for so long, given even greater problems of distance and communication. It, in fact, would've been very easy for regions of the empire to break up into independent units. Instead, however, the frequent civil wars reinforced a loyalty to the hegemonic state itself, it's just that the wars were contests over differences of who should be supreme leader.

Arguably, this is why 476 CE is the best case for the "fall" of the western empire. Because before 476 CE, Roman(ized) generals were interested in competing for the entirety of the western empire. After 476, they were content to split off to their corner of the empire, and rule it regionally, as "barbarian" kings.

Long story short, all those civil wars, from Rome to Byzantium, were the system working as designed. And as mentioned previously, look to China to see the same system in action. They lasted until 1911.