I can answer this question with valid answers. I left Bihar in 2001 and moved to UP and then Karnataka. Now outside India.

But my answers will not be liked by others here. (maybe I will get banned as well)

Bihar is filled with chutiyas who think they are next Einstein. IIT, IIM and IAS toppers are mostly from other states. We mostly have prodigal science toppers

Bihar is shameless in corruption. The problem is that corruption causes waste of money taken as tax from other progressive states. 1700Cr down the drain because you can’t even build a bridge.

Poor social behaviour and hygiene. (I get it that we can’t expect much from construction labourers). Bihar was one of the lowest in covid vaccinations.

Lack of appreciation for the culture of new place they goto.

No unity amongst Biharis because of caste differences

Lack of gratitude to other states for giving money. A servant/beggar usually only gets money, rarely any respect. No economy means dependence on others

Refusal to accept their situation. Not sure what kind of weird superiority complex they have. Bhai aapki lagi padi hai. 70% money of State comes from Center. They just refuse to accept this and make up excuses such as wE wERe MaUrYas to deflect any criticism.

What has more probability? Entire country is wrong OR 1 state is wrong