Mo clearly wanted to wait until he was rid of Mane before his signed
Yeah I was quite confident he would sign up the moment the club agreed to let Mané go. First of all, they don't appear to have gotten along so well at a personal level. It's a bit like two colleagues who work very well on the same team but just are generally annoyed with one another to the point where they feel the need to go separate ways regardless. Secondly, the club would be likely to use the funds of Mané and Minamino to have sufficient capital to make Mo an offer he'd accept.
Either way, being until '25 even then it would make sense to sign him up for the rest of Klopp's contract. I have no concerns about Mo's ability to stay in top shape until he nears 35. He's just got that sublime technique and football intelligence to play a top role for half a decade more. Playing with Núñez and Díaz, his role will change a bit with a #9 more into the penalty box and Díaz being more of a winger than a wideout striker like Mané. It will evolve a bit, but he'll play a crucial role. If Núñez is going to be flying from the get-go, he'll need Mo and Trent to be at their best for build-up play.