I think this means more than existence exists, it means that for reality itself to be ‘real’ then it must have existence ~ be something and not nothing. Upon such a foundation there must and always will be existence, and it isn’t something which itself is created, so it has no creator God, no prime cause of causality. The sentence suggest we need to have a rethink about the fundaments of what we exist in.
its philosophy is more fundamental than that of causality and physics.