What will be those 5 reasons if the BJP fails to form the government in the 2024 Lok Sabha elections?

My answer would not be exactly BJP-specific. I would try to be holistic and take a macro approach. Everything that goes up mostly comes down. There are two other outcomes. 1. Escape from the gravitational pull and get lost in space. 2. Get into the geostationary orbit and keep on rotating around the globe. Great empires fell, and great emperors fell, great organizations fall unless they make course correction. CPM was evicted from Bengal. There was a time when nobody ever thought that CPM would be thrown out. Congress has also been thrown out. The period before the emergency should have been the wake-up call for Congress.

Possibly Congress could have taken corrective steps but unfortunately, Rajiv was assassinated. After that Congress has mostly been in shambles. It doesn’t have the resources and the strength to take corrective. Amongst a few very early lessons of management, I have learned that you are best positioned to correctives when you are climbing your peak. Because at that point you have the resources and financial strength to undertake the required measures. Unfortunately, most organizations fail to see the need for correction when they are at their best or top. They feel that everything they are doing is right. They are mostly in denial and defying mode. What happens when you climb the peak, very rarely do you get any plateau. There is very little space at the top and others would keep on pushing to dislodge you. BJP did that to Congress and Congress would also do the same.

I have been to Chittorgarh Fort, it is practically invincible. But it fell many times. Because the fate of the battle was not decided by the protection of the fort. The fate of the battle was decided at the bottom of the fort hill where everything is in the open. Enemies knew that they could not breach the fort. Rajputs were absolutely safe inside the fort. They had to force the Rajput to open the fort door and fight in the open. So they laid seize for months and even years cutting out supply routes to the fort. Rajputs were forced to come down and fight in the open, where they were outnumbered.

Congress lost the battle where it was vulnerable. Congress didn’t take corrective when it was being thrown out in the state-level election. And finally, it lost out in the national election. BJP is also heading toward a similar destination. Though in this answer I would be elusive and refrain from giving pinpoint clues.

1. BJP is in denying and defying mode. This is the biggest mistake most organizations make. They downplay incoming feedback. Anybody who criticizes BJP is termed as anti-national. Whereas critics are the best friends because they point out the flaws well in advance. A good critic like Ravish Kumar would list down as many points as possible for taking correctives. Not having them around might give comfort to BJP but that would make it complacent.
2. Rajputs counted on their strength but possibly discounted their vulnerability and finally and easily got trapped. BJP also is counting on its strength but not counting its vulnerable points. An astute enemy or consultant would spot those gaps very easily. I can point out a hundred gaps from where an opposition party could make an entry. Most software houses employ hackers. Silencing critics or buying out media is the stupidest action of the BJP government. You get self-attainment and have a feel-good factor. You get captive in a self-made cocoon. Rajputs were safe inside the Chittorgarh Fort but it actually worked as a trap. Their enemies knew exactly where to attack, one single location. There was no way Raput could surprise their enemies. Shivaji Maharaj didn’t give that advantage to his enemies.
3. The fate of a battle gets decided quite often by the predictable nature of the moves And the more you play the more you watch out. In the early days, India always prepared spinning wickets since we didn’t have good attacking bowlers. However, this turned out to be a disadvantage for the Indian team for not having the opportunity to play on a fast surface. BJP is expecting the game to be played on its terms. But it's not going to be. Rajputs never prepared for battle in open ground. Shivaji Maharaj played his game brilliantly against the mighty Mughals despite having a smaller army than the Rajputs.
4. I believe the battle has already reached a tactical level and BJP is aware of it. It seems BJP knows that it is at a disadvantage point. Defending is always a difficult task because you are holding the establishments. People know where to attack. Whereas it is difficult for BJP to mount a precise attack. After ten years of rule, it is also standing where Congress was in 2014 - price hikes, increases in the cost of living unemployment, etc. At least BJP is not at any advantageous point. It's like coming out of the Chittorgarh Fort and fighting out in the open when the odds are even. BJP has been bad in economics. People may argue against it or try to justify it. But facts remain that life has become dearer. And for the common people, there are no dearness allowances. We are being forced to pay higher taxes, lesser savings, and lesser returns on savings.
5. Polarisation has been BJP’s strength. But it would be countered by the consolidation of opposition votes as evident. Consolidation is the counter-effect of polarization as well as the regressive ruling of the BJP.