If there is no oxygen in space, where the super dense singular object was suspended, then why did it explode because this reaction needs oxygen?
You don't need oxygen to make an explosion. All that is needed is that the reagents after the explosion occupy more space than those before. Going from solid to gas is a good way of getting this effect. Similarly, going from gas to solid is a good way of producing an implosion, but there is a limit on how much bang you can get from this.