Weeks of uncertainty followed before PSG announced Messi's signing on Aug. 11 on a two-year contract, with the option of a third year.
"Barcelona published a statement saying that I wasn't going to carry on, and from then I was asking myself where I was going to end up," Messi told L'Equipe.
"I was lucky to be contacted by various clubs and one of them was Paris Saint-Germain. I'm grateful to the club. They treated me well from the beginning. They showed that they really wanted me.
"I had other offers, but I have to say that we came to an agreement quickly with PSG. It wasn't straightforward because everything had to be sorted out in a short amount of time, practically from one day to the next. ... I was convinced by the project, the club's ambitions, the players they have, the squad. ... All of these factors."
In February, ESPN reported that Manchester City were monitoring Messi's situation, having been keen to sign Messi in the summer of 2020 when he tried to force an exit from Barcelona using a clause in his contract.
Messi said a year later that he intended to stay at Barcelona before the club forced the issue.
"My idea was to sign my contract and then start training again straight away," he said. "I thought everything was agreed and that only my signature was missing. But when I got to Barcelona I was told that it was no longer possible, I couldn't stay and that I had to find myself another club."
"At first glance, it's a league that is a lot more physical than LaLiga," Messi said. "Most players are very strong. But it's still early to give my opinion on Ligue 1. It's one thing watching the games, but another being out on the pitch."