The phalanx at the Punic center had been manned by expendable Gauls who were not the tactical focal point of the battle but instead were used as a drawing card for the Roman legions.
It’s hard to believe that Hannibal had only arrived in Italy a couple of weeks earlier after his tortuous journey over the Alps where he lost as many as 20,000 men. To plan and engage in a major battle in that short time is a testimony to his leadership.