Why must historylets try to pass off their baseless fantasies as history?
India reached its civilizational peak during the Guptas, a result of commerce and industry flourishing. This was an age of peace for the most part. Once the Guptas collapsed, centuries of constant warfare followed, our entire political landscape became highly fluid. Thus on paper the military of the successor states should be superior. However they were led by chimps, I think maybe 10% of our elite had even triple digit IQ. Thus Prithviraj saw exactly what horse archers were but kept his static, undisciplined infantry line for the Second Battle of Tarain, Lakshman Sena lost his whole kingdom to 18 Turkish cavalry men, Pratiharas never invaded Arab Sindh despite intending to do so because they threatened to destroy the sun image of Debul and so on and so forth.
It wasn't for a lack of will to fight that the Muzzies won, it was because utter brainlets were in charge.