I lived through it twice, once in the case of a large Canadian Company in which a guy promoted to CEO (who was already a respected CEO of a division) and the company started to erode within a few months. He was not capable of handling 9 other divisions CEOs and he got slaughtered. He was a great guy. It took 3 years to get rid of him but he had already destroyed the culture and the company was finally taken over by a multinational.
The second was with the merger of 2 multi-national food giants.
However, in Don's case I disagree with you. Getting a new CEO with biotech business experience and connections could be an excellent bet. Currently Don is trying to wear 6 hats - 2 companies and COB, CEO and President of each and he is achieving nothing. It's been 2 years since BoM top lines were released and there is no financing and plan for BoM2. Management of the Covid trial has been a farce. Zenith seems to have exciting relationships and science yet Don has not achieved any value creation or even shareholder liquidity.
The continued dilution of shareholder equity shows he has no understanding of the value of the sciience being created by his teams.
It seems very clear that Don's skill set lacks what is needed to move these companies forward.