I recently finished the season 4 of the series Spartacus and came to an understanding why Spartacua would have failed no matter how he tried..

Firstly:
1) There was no hierachy in his militia group as Crixus,Gannicus, Argo and others were considered equal.. Unlike a real army( Romans)

2) Spartacus and his militia group cannot differentiate a true Friend from a foe as personal interest thrived as slaves came from different regions. ( unlike Romans)

3)Every war no matter how passion driven needs financial backing which is absent as Spartacus and his " Soldiers " could only make do with what they scavenge from their enemies.

4)Absence of proper training and grooming: Rome had the options of sending different platoons of specialised skills to tackle the situation unlike Spartacus who just had to make do with Domestic appendages converted to warriors and make shift fighters..

5)Distractions. Spartacus had the major distraction which should not occur in any military. Soldiers having personal relationships e.g Naevia and Crixus can cloud good judgement as sentiments tend to arise.

6). Spartacus had an inflated ego: This is equally seen in Gannicus and Crixus. The feeling of being "Gods of the arena" is not only inflated but could amount to nothing faced with the brute strength and strategic prowess of the roman army..

CONCLUDED.