In the US, there are states which always vote Republican, called Red states and states which always vote Democrat, called Blue states. And cities which have big and many universities almost always vote Democrat, and states with such cities are often Blue states.
Delhi has JNU and DU where two generations of Delhites have now been incubated. They hate Sanatan Dharma and curse their parents for their birth in India, instead of, say, USA. Delhi also has a concentration of looting bureaucrats and their children from all over India. It also has the biggest concentration of tax thieves and those who benefited from the black money in real estate.
So, Delhi is firmly a Blue state. Scoring 42% in it is remarkable. But BJP must not waste much time on its analysis. It should now concentrate on Gujarat where an insipid, aloof CM is undermining its foundations.
States need Caste alliances. BJP is losing Red states because its CMs start concentrating on pleasing the Liberals immediately after taking an oath, instead of working on Caste alliances. Over centuries, many have tried to wish away the Castes, and have come to grief as a result. BJP should focus on Castes in Gujarat, Rajasthan, Maharashtra, and MP; and go out firing on all cylinders in West Bengal. Bihar is in the bag, because of the Caste alliances in place. They must be nurtured and nourished.