I think Liverpool recruited a new goalkeeper not to replace Alisson, but Liverpool wanted to recruit a new goalkeeper to be Alisson's cover. I am sure that Liverpool will not sell Alisson because he is a good goalkeeper.
Alisson is bad in this season, but it's unfair to kick him just because underperform in one season, he already played for six years in Liverpool, Liverpool shouldn't forget with his dedication for last six years.
But, if Liverpool want to sign James Trafford, they need to sell either Becker or Kelleher. Considering Saudi Arabia want to pay high to get Alisson, this might be the reason why Liverpool think this gonna be a good trade.