I believe that the Erling Haaland transfer is going to be amazing for Manchester City. As they reached an agreement with him already, they would get prepared for sending Gabriel Jesus from the team at the same time. Actually they would have thought of keeping him as a substitute too. But I assume he wouldn't like to just rot there as it wouldn't be easy to compete with a striker like Haaland. We will see if this Haaland transfer will bring the CL title also.
I think that in the end there were not that much big clubs interested in Haaland that were really able to meet the huge financial demands that Haaland and his team had. There were some rumors that FC Barcelona wanted to sign Haaland too but the whole packaged would have costed them more than 300 Million € and Barca already has more than 1,3 Billion € of debts so if they would have really tried to sign Haaland that would have been absolutely crazy. I also read that FC Bayern was seriously consiering to sign Haaland to as a replacement for Lewandowski who is already 33 years old but they just did not want to fulfill all his wishes.
I also don't think that the signing of Haaland means that ManCitiy will now definitely win the CL title. He is only one player after all and he still has to prove that he is one the best. He also had so many injuries this year.