Wars of I BC century and Roman laws that put people into slavery for debts had brought hundreds of thousands of slaves into economy bringing cost of labour close to zero. Conquest of Egypt and North Africa flooded markets with cheap grain.
That market disruption made artisan shops and small farms unable to sustain/compete on the market with larger enterprises based on slave labour.
Majority of citizens of lower class had been then entitled to free food and free entertainment (bread and circus). It was necessary for keeping their votes and for keeping appearances of the republic. (Even what we call Roman Empire were still nominally a Republic with Senate and elections held for various offices every year at Fields of Mars).
I recommend everyone reading Rubicon by Tom Holland. https://www.amazon.com/Rubicon-Tom-Holland/dp/1400078970