1. It was not Fallen's fault, but he was part of the team that conceived those terrible losses. So he might not be the direct problem itself, he's part of the bigger problem. You can't blame everything on the IGL, it should be 40% IGL and 60% is the players and their mentalities, which Liquid has always been lacking since 2020.
2. First, Fallen is 30 years old already. That's already really close to retirement age for a pro in any esports. Stewie is a very moody player and he became extremely unstable during the period of 2020-2021. Plus, they are from NA, a non existent region with very low competition. CIS is much tougher and you always need to stay in shape to compete with other T1 teams. Also, the 4 youngsters in Gambit can motiate Hobbit a lot, but do you think players like Naf & Grim can motivate Fallen & Stewie when they are down??
3. Liquid had ALREADY tried Fallen as IGL for few months, and it didn't work that well. Fallen can't even IGL on certain maps like Nuke (because hes very inexperienced with it) so thats why they switched back to Stewie/mix. I really think the best combination for Liquid going forward would be 2 veterans (Naf, Elige) and 3 young blood who are hungry for titles (Grim, x , x).