"The highest treason a crab can commit is to leap for the rim of the bucket."

Source: Steven Pressfield, The War of Art

In other words...

Groups suffering together can sometimes seek to reinforce each others' suffering, in order not to be alone in it.

When someone tries to leave or demonstrates that they can make their life better, it shows others suffering that we too can make our own lives better.

Sometimes the reaction to this is positive and transformational--"wow, I could live a better life too!" but sometimes, and this is Pressfield's point, the reaction can be very negatively charged. We may resent that person for escaping suffering, because it challenges our belief that the suffering was necessary, meaningful, or 'the way things are.'

So when a fellow crab escapes, it makes us question why we haven't yet escaped. "You mean I could have jumped out of here this whole time?"

Attaching shame or guilt or our whole identities to the experience of suffering, makes us dig in our heels, and instead of freeing ourselves too, we get angry with the escapee and align ourselves against them with everyone still in the bucket. "No, I want to be here! I should be here! They're cheating! Right everyone?"