The argument you presented is based on a specific definition of God as the creator of the Universe. If you define God in this way, then it follows that if the Universe exists, there must be a creator, which you identify as God. In this context, belief in the existence of God becomes a matter of accepting the given definition.
However, it's important to note that beliefs about the existence of God can vary greatly across different religions, spiritual traditions, and philosophical viewpoints. Not all individuals or cultures define God solely as the creator of the Universe. Some people conceive of God as an impersonal force or energy, while others may see God as an abstract principle or a manifestation of divine love and consciousness.
Belief in the existence of God or any supernatural being often goes beyond mere definitions and can involve personal experiences, cultural upbringing, philosophical reasoning, and faith. For some individuals, faith and personal experiences are sufficient evidence to believe in the existence of God, while others may seek empirical evidence or philosophical arguments to support their beliefs.
The nature of belief in God is complex and deeply rooted in human history, culture, and personal experiences. As a result, discussions about the existence of God involve a wide range of perspectives and approaches, and people may arrive at different conclusions based on their individual worldviews and understanding of the concept of God.