Nothing means it's not a thing. This means you cannot imagine nothing, but I don't thing that it invalidates the question why something exists. Another related question is whether everything could be different, for example the laws of physics, fundamental constants, etc. Other question is why the laws of physics seem to be regular and why we don't have a chaos instead. Even if we knew all the laws of nature (which I doubt) we won't be able to explain why they exist and why they are as we know them.
Ah, the fine tuning argument. Well, even there it helps if you know some physics. It may or may not actually provide a final answer, but it still will beat some navel-gazing based on ignorance.
Because here's a fly in the ointment when you actually do know some physics: When you express them in Planck units, c is 1. G is 1. Planck's constant is 1. And so on.
Those funky, seemingly arbitrary values for those constants in SI or Imperial units (e.g., G=6.67408 × 10
-11 m
3 kg
-1 s
-2) are just an artefact of the arbitrary units that we chose for those systems. In Planck units they're 1.
And Planck units are the units that the universe actually "works" with. E.g., the maximum information you can pack in a spherical bit of space (the maximum, as it turns out is a black hole) the number of bits of information equals its surface in Planck units. No conversion constant involved. Or rather, again, the conversion constant is exactly 1. You're probably starting to see the pattern already.
So, anyway, in Planck units those constants are exactly 1. Worse yet, because of how they're calculated, they'd still be 1 even if you picked a universe with a different value of c or G in our units.
So, hmm... CAN they be anything else? Because it's kinda nonsense to ask why is G=1 unless you can make a reasonable case that it could be anything else.
Similarly for stuff like particles, energy levels and the like, they're field resonances. So, again, CAN they be anything else? I mean, think of a guitar string. What resonances can it have, given its length? Yeah, no fine tuning will get you a 1/3.14 wavelength as a resonance.
Basically, unlike some other members, I'm not against philosophy or thinking about stuff per se. But I AM saying that ultimately you have to do the above: have science inform that thinking, if you want it to be worth beans.