Both the parties have faced horrible defeat in the 2019 elections. BJP hasn't won a single seat in all over the AP, and JanaSena has managed to get only seat. In this case, both the parties have failed to impress and attract the people.
People have a precise opinion on BJP. Mostly BJP is not even considered as a main political party in AP. Jana Sena party is always a question mark for the people to understand the ideology of Pawan Kalyan.
Now they decided to sail on the same ship expecting good fortune. They both are in great need of each other, BJP is ruling the country with tremendous majority, but fighting for its survival in AP. In this case, it needs a personality that can lift their party from the downfall. They need a crowd puller to attract the people and to pass their voice to the public. Honestly speaking at present conditions, no person in AP cares about BJP. Considering all these aspects, BJP looks towards Pawan to change the situations completely.
Pawan is also in great need of BJP support. So far, form the formation of the Janasena, Pawan has never sailed alone. He has taken support from every party in the state, expect YSRC. He traveled with TDP, CPI, BSP, and now BJP.
Maintaining the party till 2024 elections without any power is not an easy task for Pawan. It all depends on the commercial aspects to run the party. In this case, he definitely needs some support, and that support comes in the form of BJP. They believe Janasena's force and BJP's strength can lead them to rule in 2024.
If everything goes according to the plan, it can benefit them. If it misfires both the parties have to pay the price. The effect will be more to the Janasena than the BJP.
BJP has nothing to loose in AP, but Jana Sena has a lot to achieve.
No one can predict Pawan's actions. He never moved with any party constantly. He changed according to the situation to stay in a comfort zone. Still, there are four years for the assembly elections in the meantime anything can happen.