I think, this universal destruction has been caused by the irresistible course of Time. This dreadful slaughter was inevitable, since it has not been brought about by human agency!
पन्ये लोकविनाशोऽयं कालपर्यायनोदितः॥ अवश्यभावी सम्प्राप्तः स्वभावाल्लोमहर्षणः।