Bjp is currently the only consolidated and organised party on the national level. With PM Modi as a focal point they've managed to organise and optimise decision making process. This makes their decision making capability much more efficient and faster than any of their opponents. They also make it a point to reward only those who give verifiable results. For the tickets to contest UP elections, the BJP set the criteria of x number of follwers on social media. BJP Applicants vieing for the tickets had to prove that they had the reach and soft power to influence voters. This sort of internal competition makes merit ascend the organization ladder.
You take massive resources in the form of financial, man or soft power and combine it with an organised machinery with efficient decision making process and you get an idea what BJP has managed to achieved.
However, therein lies the problem
. For a focal point you need a set of definitive ideas and actions that would rally people to your cause. Indias diversity and abundance ensures that statistically more people either don't care or oppose those definitive set of ideas.
Human beings are fickle and are not persuaded by logic but emotions, tell 10 people the sky is blue and approximately 4 will agree implicitly, 4 will oppose and 2 will tell you the earth is flat.
The problem is that the supposed leftists opposing party on the national stage like congress have been nothing but a disaster this last decade. No other political organisation has been able to appeal to so large a number and consolidate around a central idea. Multiple factions withincongress and their insistance with no central focus other than the Ghandhi family makes the entire machinery even more inefficient and discourages merit from moving up the ladder.
Specialized political parties like on the state level are a different beast though. To put it bluntly, voters prefer to vote for BJP on national elections, State parties on state elections and so on down to city level corporation elections. A national party like BJP cannot be as attuned to local problems and needs as State parties can.
