Inflation naturally predicts a very nearly flat universe. (judithcurry.com)
However, for many years, it has been evident that there is less than half of the amount of matter in the universe to account for a flat universe. (religion.blogs.cnn.com)
A Big Bang model in which there was just enough matter to equal the critical density to account for a flat universe would have provided that. (religion.blogs.cnn.com)