Aligning top-management is toughest and most important cookie there is (blackmail never works in the long run). Especially now when they are already treated as two separate entities by the inside top-boss (first PG and now LBT) / management AND the outside world for a couple of years.
Design is competing with AMD, NVIDIA, BROADCOM, Apple and the rest of the fabless designers and Design has no influence on the operation and success of Foundry. Foundry is competing with TSMC and Samsung, and has no influence on the operation/success of Design.
So, there is no "emotional reason" to keep both sides connected. Even worse, the profit of Design is used to compensate for the losses/capex of Foundry, probably for many years to come. This could easily create resentment and "despair" at Design, as they may feel a complete loss of strategic control. Good competent people hate loss of direct control about their (professional) future, so they eventually leave and look for conditions/environment where they sense again control about their (professional) future. Less competent people stay and both sides, Design and Foundry, simply become less competent over the years.
Tough cookie for LBT, INTEL has a disjoint cultural alignment it seems to me. Unfixable besides a real break-up?
https://companyculture.com/about/