in my experience, people higher up the chain are much more at risk of being let go at any time
I agree. And the insecurity that these managers feel makes them very poor leaders. They tend to be overly subservient to higher-ups and just pass all management decisions down the chain without too much thought. And they like to punish any disagreement (no matter how reasonable) from their subordinates. Insecurity is the opposite of a culture of trust. And where there is no trust, there is no real leadership.