Because it was a very different kind of a singularity than what you find inside a black hole. The essential physics were entirely different. There were no 'in-going' geodesics, only 'out-going' ones in time. For black holes, you only have 'in-going' geodesics. Also, black hole 'solutions' are part of the local geometry of space-time and are embedded objects. The Big Bang singularity is part of the global geometry to space-time and is not an embedded object. As to how matter escaped from the Big Bang singularity, it's simple. Matter had no choice. These were the only geodesics possible at the time. Also, although local 'horizons' were present, they were constantly growing in size so that today they have all merged together to form the one that we see as the horizon to the visible universe.