If I remember correctly, there is a passage way from the Baudelaire mansion to Esme's penthouse. And when the Baudelaire's were underneath the one for there house, it was locked from their end and they had to break the lock right?
So I'm guessing when the fire started at the Baudelaire mansion, the passage way was locked from underneath to keep them inside the house and wasn't unlocked again till the Baudelaire orphans came across it in the EE. Right? Has this been mentioned before? I'm pretty excited to have discovered that little detail.
And because I am sure the Baudelaire parents knew the passageway connected to Esme's apartment, they didn't know she was evil? But they probably did to have stole poison darts from her. Just weird to have a home with a secret passage underneath leading to a nemesis.
The secret passageway under the Baudelaires' mansion didn't always lead to a nemesis. It led to 667 Dark Avenue, and there are hints in the U.A. that that was a safe place for V.F.D. The way out of the passage on the 667 end used to exit next to the penthouse apartment, and while we don't know who owned it before, we know that Jacques encouraged Jerome to buy it, and that Esmé probably married Jerome to get control of the passageway. I'm sure the Baudelaires knew that the passageway was there, it's simply that Esmé hijacked it so it couldn't be used in their favour. The idea that Esmé might have locked the trapdoor beneath the Baudelaires' home to prevent them from escaping is a compelling one and probably something that Handler intended, yes.
You know, a certain amount of this is addressed in what was the top thread in this subboard at the time you posted, the death of the Baudelaire parents thread. You might want to look around a bit more in future before asking questions like this; you might find some more evidence to support your ideas. I do accept that the number of threads is a bit overwhelming, though.