Why did my meringue deflate and go soft? I used 8 egg whites with sugar and beat it. It was so stiff that I could actually maybe cut it with a knife and make a sculpture out of it.

I preheated the oven to 150 degrees and baked it at 140. The meringue deflated and was soft and quite a disaster.

Can anyone please tell me where I went wrong? What made it soggy and deflated? It did not even start to crack. There was not a single crack in the base.
How long did you cook it for?  If it did not form a good crust in the oven it would deflate.  If you used 140 on fan forced oven it could be too hot, which would rise and brown the outsides without forming a crisp crust.    

Usually the rule is to turn the oven off and let it cool completely before removing from the oven, but without the recipe or knowing if there was an intention of "softness", its hard to give specifics.