Before Leo entered Beastnet for the first time, the Flaming Lion God had already decided on Lionel's future thanks to Lionel's potential.
So, he was hoping that Leo would allow him to become Lionel his apostle.
"I know Lionel has good potential; however, if he becomes God's apostle, it would be wasted."
Leo could hear Flaming Lion God's inner thoughts and knew he only had good intentions towards Lionel.
However, he didn't want Lionel to become a God's apostle because in Leo's opinion, becoming a God's apsotle is no different than killing Lionel's future path of going against the Gods.
As a God's apsotle, he should obey his God and the moment he goes against his God's orders, only death awaits him.
Of course, if it was others who didn't have any potential, Leo wouldn't object to him or her becoming the Flaming Lion God's apsotle because they would become strong and could become the guardians of the world.