Yuki has his seat because of Honda and Honda is leaving for Aston Martin in 2026 and I am confident Yuki will be gone then, as well. So Red Bull was never going to promote him for just a year when they can hope that Liam will be able to hold his own for multiple years.
Toto still has PTSD and FOMO over Max and believes (or at least prays) that Kimi is the next Max Verstappen. George is also comfortable in the team and looks like he will be able to comfortably take over as Team Leader in 2025 so the team only needs to "worry" about one new driver instead of two.
And that concern is why I think they passed Carlos Sainz over. They did not want to have to integrate two new drivers into the team at the same time, especially one who is a rookie.