There are several perspectives to address this question. I personally believe they have more overlap than not, but please note the later sections of this answer may contain some less conventional opinions.
Just World Theory
We could say that people are motivated to believe in a world that is inherently, predictably fair (the just world hypothesis). This allows them to predict and control their own safety and future (mis)fortune. For example, if a person endorses a just world, and they believe that they are a good person, they can believe that tragedy will not befall them as a manifestation of justice (Lerner, 1965).
If something terrible happens to a victim with no fault of their own, that serves as a contradiction to the just world hypothesis, which causes cognitive dissonance. To alleviate the dissonance, people can re-appraise the situation and assign blame to the victim--to keep the just world belief. Experiments find that just world beliefs and victim blaming are positively associated (Reichle et al., 1998).
The just world hypothesis can arguably be considered a cognitive bias, and it fuels cognitive biases such as those involved in victim blaming, such as defensive attribution (Shaver, 1970).
Social incentives
When people who are dominant or similar to the observer engage in cruelty, that may lead them to justify the behaviour because people tend to conform and defend those they like. If you defend a perpetrator, you have to blame the victim to prevent cognitive dissonance. For example, studies find that men are more likely than women to blame female victims of sexual assault because of such attribution biases (Grubb & Turner, 2012).
Moral Reasoning
Social influences aside, is belief in a "just world" causally linked to victim blaming? I believe the construct may be a bit too broadly defined. Just for some perspective, Kohlberg's theory of moral development (Kohlberg & Hersh, 1977) divides moral development into three stages (with two sub-stages each), and I think the first 'preconventional' stage aligns with the kind of just world perspective that leads to victim blaming. Preconventional morality follows rigid right-wrong rules that lead to reward, punishment, or at most, reciprocity; which are particularly ripe for developing beliefs that 'good' deeds are rewarded and victims are 'weak'. There is some evidence for a negative relationship between stage of moral development and the justification of aggression (Berkowitz et al., 1986).
Maybe there are some other psychological mechanisms than simply endorsements of a just world, i.e. third variables, that contribute to the experimental effects. For example, can it be that the cognitive goal / motivation behind endorsing a just world is a more important variable than the belief itself? It might be too speculative to link two different areas of research, but I did want to mention how the just world belief construct seems deceptively simple and may be imprecise.
Object relations theory
The psychodynamic theorist Melanie Klein postulated a 'death instinct' that drives destructive impulses (Klein, 2011). The theory offers an explanation, though one difficult to demonstrate as correct, for blaming the victim: it is a case of the observer engaging in projection of their negative emotions and drives: fear of an unjust world, guilt for complicity, their weakness or helplessness, or their own aggressive impulses. This can fuel the many cognitive biases, motivations, or traits mentioned above as attempts to maintain ego stability and emotional equilibrium. I know this forum is not extremely enthusiastic about psychodynamic theory, but object relations has some substantial scientific support (Svrakic & Zorumski, 2021).
References
Lerner, M. J. (1965). Evaluation of performance as a function of performer's reward and attractiveness. Journal of personality and social psychology, 1(4), 355.
Reichle, B., Schneider, A., & Montada, L. (1998). How Do Observers of Victimization Preserve Their Belief in a Just World Cognitively or Actionally? Critical Issues in Social Justice, 55–64.
Shaver, K. G. (1970). Defensive attribution: Effects of severity and relevance on the responsibility assigned for an accident. Journal of Personality and Social Psychology, 14(2), 101–113.
Grubb, A., & Turner, E. (2012). Attribution of blame in rape cases: A review of the impact of rape myth acceptance, gender role conformity and substance use on victim blaming. Aggression and violent behavior, 17(5), 443-452.
Kohlberg, L., & Hersh, R. H. (1977). Moral Development: A Review of the Theory. Theory into Practice, 16(2), 53–59.
Berkowitz, M. W., Mueller, C. W., Schnell, S. V., & Padberg, M. T. (1986). Moral reasoning and judgments of aggression. Journal of Personality and Social Psychology, 51(4), 885.
Klein, M. (2011). Envy and gratitude and other works 1946-1963. Random House.
Svrakic, D. M., & Zorumski, C. F. (2021). Neuroscience of Object Relations in Health and Disorder: A Proposal for an Integrative Model. Frontiers in Psychology, 12.