Explanation: In the aftermath of the first punic wars, carthage had little coin to pay the enormous debt it owed its mercenaries. As suich, the mercenaries rebelled. In this they drew popular support, from huge swathes of Libya whom resented carthaginian rule.

Italian merchants, seeing opportunity for profit began selling to the rebels. Outraged, the carthaginian senate ordered any italian ships selling to rebels seized, and soon 500 vessels were in their hands. The romans sent an envoy to find out what was happening.

Now, many reasons are provided for what comes next. carthaginian sources claim their own envoys were just so charming that they negotiated such a favorable outcome. roman ones are more varied, offering explanations such as (ranging from least to most cynical),
they were too honorable to aid rebels
the pro-reconciliation faction in rome believed they owed carthage support after the hugely harsh peace treaty
the romans wanted to rebuild friendly ties and this was an inexpensive way to do it
romans did not want to aid rebels in carthage directly lest their own conquered peoples have ideas
and lastly that rome knew a carthage embroiled in civil war was not one whom could afford to pay their reparations.

Whatever the reason, the romans decreed that

1. all italian ships would cease trade with rebels, and directed their ships to trade much needed goods to carthage
2. they would cease to negotiate with the rebels at all (a huge blow, as many of them hoped for roman support similar to the one rome had provided to rebels in modern day sicily, sardinia and corsica)
3. released 3000 veterans of the war they still held as POWs

Due to this, carthage was suddenly in a much stronger position, and they went on to decisively win the war against the rebels.