Bake cracked during oven spring

Most likely it needed a longer final proof. If your proofing temperature is lower than recommended (usually 72-78) it can take much longer than indicated in a recipe. You want the dough to spring back just slightly when you poke it with a finger--it shouldn't be too firm or it's underproofed and this blown loaf will happen. Conversely, if your fingerprint stays, it is likely overproofed which can lead to other problems. In all cases, it's still edible! Good work and bake on!