It indicates that love and even wisdom without force are incomplete. As long as India kept the balance of these three integral aspects of human nature, that is wisdom, love and strength, it was invincible. But when it discarded strength under Buddhist influence and then love under the influence of Shankaa, it was left only with knowledge. But knowledge without love and strength is ineffective. We discarded Shakti and therefore the Shakti discarded us like in the story of Bhringi Rishi.
Islam has caught the force aspect, Christianity caught love. Both came to India to get what they lacked, – knowledge. India gave its gift of knowledge generously and freely but paid it with its own life because by then the spell of Mayavada had taken it over and both love and strength had diminished. Though the later bhakti movement revived love but mainly in a narrow movement of love towards God who was other than the world He made. Tantra revived the worship of Shakti but again ended up seeking personal Mukti. Had India followed the teachings of Sri Krishna it would have never been overpowered.
But perhaps this too was God’s Will to eventually help Islam and Christianity to discover a greater, deeper Truth that India guarded within its boundaries.