Ask what India eats and most people picture a vegetarian plate. The national survey says otherwise. In NFHS-5, only 16.6% of men and 29.4% of women said they never eat fish, chicken or meat — and 57% of men and 45% of women eat it at least once a week.
The country divides by region rather than by virtue. In the southern states, about 5% of men and 8% of women never eat meat. In Haryana, Rajasthan, Punjab and Gujarat, roughly half the women and a third of the men never do.
So Diwali looks like two different festivals depending on the kitchen. In much of Tamil Nadu the day doesn't properly begin until the mutton is on the stove. Across much of the north it is kept without a trace of meat, exactly as it always has been.
Neither one is the deviation. The national picture is an average of two traditions that were never the same tradition — and that average has mostly been reported in the voice of whichever kitchen got to speak for the country.
Both are Diwali. The plate belongs to whoever is eating from it.