[3PS]

So this is a little nuanced. It's true that quantum systems collapse on "observation", but that doesn't actually mean "observation by a sentient entity". It could really just be any interaction with the outside environment. (This is why qubits have to be kept incredibly well-isolated.) We don't really fully know exactly how this collapse works, and related speculation is generally classified under the measurement problem [1]. But it's true that one of the key points of Schrödinger when proposing his thought experiment was that the notion of measurement or observation was not fully defined under the Copenhagen interpretation.

Side note, it's not that the cat is observing poisonous gas, but rather, that a Geiger counter is set to detect whether a radioactive atom decays or not and triggers the release of some poisonous gas if so. So, classically, Schrödinger's cat would be either alive or dead 50% of the time, not 100% dead. There are plenty of alternative ways to reconcile this classical view with quantum mechanics. Perhaps the simplest and most well-known is the many-worlds interpretation [2], which states that both events occur, just in different timelines, and we don't know what timeline we ended up in until we open the box. (Of course, it is ridiculous to speculate as to which timeline "we" end up in before the experiment is carried out, because the people in both timelines would still be "us" - this can get awkward to think about.)

[1] https://en.wikipedia.org/wiki/Measurement_problem

[2] https://en.wikipedia.org/wiki/Many-worlds_interpretation