Some become leaders as a clear part of career ambitions. Others do so because it unintended becomes part of their role. Maybe the start-up hit it and scaling up put you in a leadership role. maybe a project got you committedly engaged and others started to follow, or maybe your own boss saw something you were not aware of yourself. For whatever reason you suddenly see yourself standing in front of others and realize - “they see me as their leader” - you are wise to take the job seriously. Others now lean on you, need you and hopefully trust you to support them in doing a good job in your mutual interest.