I think the official explanation is that Jesus was quoting one of the Psalms and he was fulfilling the prophecy, the Psalm was about the enemies of God mocking the faithful. And, becuase he was taking on all of humanity's sins at that moment, so he was giving a lament as a genuine sign that he was a fully corporeal human undergoing this trial. Also, saying that God had forsaken him isn't a loss of faith, just like the Psalm isn't losing faith in God, it's more like being a weepy baby and being overly dramatic whenever something goes wrong in your life.

The real explanation is that Jesus was a crazy white boy who talked mad shit and got executed by the Romans while all his bros stood by and watched. He thought he was the reincarnation of King David and he would kick all the Romans out of Jerusalem but ended but on a cross, so he probably did curse God as he was dying for all the bullshit that happened to him. Whoever wrote the Book of Mark then substituted in a quote from the Pslams because he didn't want Jesus' last words to be "Fuck you God". As a result the early church had to justify why Jesus would be talking to God when he was also God and ended up going with the Trinity.