>If instead of detecting the smoke (e2e) you try to monitor all the data like pressure in gas pipes, all the pipes fittings, how many lighters are in the building and where, etc, you will wake up every night 10 times for nothing

Without this you'll always be awoken by smoke, and at that point it's too late... there's already a fire. However, if you can monitor other things (gas pipes, lighters, etc), you might be able to remediate a problem before it starts smoking or burning.

There's no one-size-fits-all. Start with some obvious failure (e2e tests/checks; aka smoke), and when you root-cause, add in additional checks to hopefully catch things before the smoke. However, this also requires you update (or remove) these additional checks as your software and infra change... that's what most people forget, and then alert fatigue sets in, and everything becomes a non-alert.