It's challenging to determine the exact reason without more context, as people's motivations and behaviors can vary greatly. However, I can suggest some possible reasons why your ex might be taking credit for you meeting your new boyfriend:
Seeking validation: Your ex might be trying to boost their own self-esteem by taking credit for your happiness. They may want to feel like they had a significant impact on your life even after the relationship has ended.
Jealousy: Seeing you with a new partner could trigger feelings of jealousy or resentment in your ex. Taking credit for your new relationship might be their way of trying to downplay its significance or make themselves feel better.
Attention-seeking: Some people seek attention and validation through various means, including exaggerating their influence in others' lives. By claiming credit for your relationship, they might be trying to gain attention from mutual friends or acquaintances.
Regret or remorse: If the breakup was difficult for your ex, they might be trying to rationalize their actions by convincing themselves and others that their influence led to your happiness with someone new.
Manipulation: In some cases, people may try to manipulate their ex-partner's emotions or decisions by claiming credit for their successes or new relationships. It can be a way to maintain a level of control or influence in your life.
Misinterpretation: It's possible that your ex genuinely believes they played a crucial role in introducing you to new people or events, even if the reality is different.
Regardless of the reason, it's essential to focus on your own feelings and well-being rather than getting caught up in your ex's actions. If their behavior becomes bothersome or toxic, it may be best to distance yourself and maintain healthy boundaries. Building a new relationship is a positive step forward, and it's essential to surround yourself with supportive and understanding people.