The former Liverpool manager terminated his contract by mutual consent after winning the Club World Cup in December and the side has been transformed under new boss Leonardo.
"Some players were giving their all, some were not, but that happens after a year of great success," Benitez told Marca.
"President Massimo Moratti knew how we were working and the difficulties we faced every day. He hoped things would go for the best, but we simply didn't have the conditions needed to continue, so we agreed to rescind the contract.
"My adventure on the Inter bench had started well and we played good football, but injuries changed everything, including the internal dynamics of the team. Week after week, opinion on us changed based on the latest result and the papers continually speculated on my replacement."