The Belgian goalkeeper signed with Club Brugge this summer after six years at Anfield.
"If I could really fight for my place, I might have stayed," he told Het Belang van Limburg.
"But if I had ended up in goal if Alisson picked up an injury, I would be allowed to push 10 shots out of the box.
"Then Alisson could immediately claim his place again, and even if he pushed the ball into his own goal, he would still stay [in the starting XI]. What sense did it make for me?"