My DM gave us a pass and I feel disappointed

So I'm a long time fan and playing my first campaign. First big quest and we're in a fortress.

Pretty spent after an encounter and some traps. We see a sleeping BBEG in the way of our finish.

Cast pass without a trace to sneak past. Fighter in heavy rolls a nat 1 on his disadvantage.

So it's 1 + 1 dex +10 pass without a trace = 12

BBEG passive perception is 10. We sneak past.

WTH? I mean sure my PC is happy but I feel somehow disappointed in our DM giving us a pass.

I've DMd before and would've definitely woken up the boss.

I feel like DM gave us the pass cause it could've been a TPK.

Thoughts?

Edit:

Thank you everyone for your thoughts.

I was caught up in the homebrew rule of auto fail nat1s that is NOT in the PHB.

Rules as written we earned that easy win by taking advantage of the bosses low perception and spending a spell slot on pass without a trace.