~~Most~~ Many people are complete immature dicks.
Self-evaluation maintenance theory
Tesser's self-evaluation maintenance theory (SEM) suggests that individuals engage in self-evaluation not only through introspection but also through comparison to others, especially those within their close social circles. When someone close to an individual excels in areas they value, they may feel threatened and act in ways that downplay their achievements. This mechanism can partly explain why individuals may attempt to pull down those who achieve more than themselves as a way to protect their own self-esteem and social standing. Emotions such as envy may be generated when individuals feel threatened during self-evaluation. This can lead to a desire to diminish the well-being of others, particularly when their success highlights the individual's own failures or inadequacies.
Relative deprivation theory
Relative deprivation theory proposes that feelings of dissatisfaction and injustice arise when people compare their situation unfavorably with others' situations. This sense of inequality, rooted in subjective perceptions rather than objective measures, can deeply influence social behavior, including the phenomenon of crab mentality. When individuals see their peers achieving success or receiving the recognition they feel is undeserved or unattainable for themselves, it can trigger actions aimed at undermining these peers' accomplishments. The concept emerged from a study of American soldiers by Stouffer. Soldiers in units with more promotions were paradoxically less satisfied, feeling left out if not promoted themselves, despite better odds of advancement. This reflects how relative deprivation fuels dissatisfaction by comparing one's situation to others. By "dragging" others down to a similar level, individuals might feel a sense of satisfaction. Thus, crab mentality can be viewed as a response to perceived social inequality, where pulling others down becomes a strategy to cope with feelings of inadequacy or injustice.
Zero-sum bias
Zero-sum bias, where individuals perceive that they can only gain at the expense of others, may contribute to crab mentality. This bias is rooted in a fundamental misunderstanding of success and resource distribution, leading to the incorrect belief that success and resources are limited and one person's gain is necessarily another's loss. Such a worldview fosters competitive rather than collaborative social interactions, encouraging behaviors that aim at hindering others' achievements to protect one's perceived share of limited resources, like crabs in a bucket. In Daniel V. Meegan's study, researchers found that students expected lower grades for peers after seeing many high grades already awarded, despite being in a system where high grades are unlimited. This illustrates how people often view success as a limited resource. Thus, when they see their peers successfully "climbing out of the bucket", they may try to hinder their progress to ensure their own chances of success remain unchanged.