Change is a normal thing when it comes to portfolios, and he should act upon each strategic change in a quick manner in order to re-align his portfolio

Not all strategic changes impacting his portfolio need to be taken care of; he should prioritize the change and only accept the ones with high priorities

Help him to align his portfolio and manage it correctly in order to decrease the number and scale of changes

Inform him that this is abnormal and that he should re-do the planning for his portfolio; even if it takes time and resources, but it will help him a lot for the rest of the portfolio life cycle