Mane left the Reds in the summer for Â£35m.
â€œI think he has been here for a couple of years and I think at some point he thought he did not have the love that he needed really, here at Anfield," Diao told the Liverpool Echo. â€œI'm not talking about the fans, for him I think it was more with the manager.
â€œThings weren't really going on as they should be so that's why he decided to go for a new challenge. I think as a top player, every time you stay 4-5 years at a top club, sometimes it's good to go for a new challenge."
On Darwin Nunez replacing Mane, Diao also said: â€œEveryone knew it would be hard.
â€œFor any player coming in, it would be hard to take his place. I think people didn't realise the hard work he has been doing here at Liverpool.
â€œIt's normal, he's a top player. He's been one of the best top three players, if not the best, over the past four years in the world. He's proven on all levels. Of course it would be hard for any player to come in and fill his space. It's going to take time."