The necessity of reality and the principle of sufficient reason

Hello Rabbi,
I saw a discussion on YouTube between you and Zvi Yanai about evolution.
There you start from the assumption that this universe is not the necessity of reality and in any case, according to the principle of sufficient reason, we will need to reach a factor that is the necessity of reality.
I wanted to ask why?

After all, I can assume that God does not exist, just as I can assume that our world does not exist.
What is it that you hate?

B. Moreover, if we can even assume that this world is the necessity of reality according to our experience, then we can never lose energy, only convert and change its form.