The difference between "how" and "why" doesn't seem very meaningful to me. For example- why does water boil? It boils because molecules gain enough energy through heat to transition states.
In that same sense, OP's question
why there is something instead of nothing.?
There's a non zero chance that we eventually understand the mechanisms behind the big bang and can explain how nothing turned into something. Therefore we will be able to explain the why, no?
The problem with the question of why is that you can always ask why again. Say we do understand the mechanism of the big bang. You can still ask "why" about why things are that way. Which is why in my view that's still more of a "how?" "Why" is more of a question for philosophers than scientists imo.
I think the "why" exists only with the idea that the universe is directed in some way. e.g. "How can I see around my room"? Photons. "Why"? Because I turned on the light.