Factions of the Tory party are probably lining up Braverman as Party Leader in Opposition because they know they will lose and they need a vile, vicious attack dog whilst in opposition that knows no bounds. She’s perfect for the job - head and shoulders above any other candidate.
Sunak knows this and is leaving her in place as she will in the interim do the whipping up of the fear of ignorant base with her populist rantings which will minimise the extent of their election loss.