Lucas left PSG in January after becoming fed-up with being frozen out by Emery.
He told France TV Sport: "I did not understand. Until today I do not understand. I had my best season the year before, second top scorer, a lot of assists, the most played player, and all of a sudden, the season started without me playing. I was at home. I went to training, and at matches I was at home. I was not even in the squad.
"Unfortunately, these are things that happen in football. Whenever I was training, not being called for the match and coming home, I took my son in my arms and forgot all the problems. It gave me a lot of strength to continue working, to give my best in training. I knew it would give me a new opportunity in Paris or in another club. That's what happened with Tottenham. It served me as an experience, it reinforced my maturity."