Why is the output from this astable 555 the reverse of it's simulation?
You did something wrong. I reproduced your circuit in LTSpice and got this:



Output is high for the better part of an hour. Somewhere before 2800 seconds, it dives to zero. The blue trace tracks the capacitor voltage, by the way.

I suspect you forgot to checkbox "Skip Initial Operating Point Solution" in the Edit Simulation Command dialog box!

If I do the same, I get this:



Look familiar in any way?

For reference, the circuit: