From what I could gather from UPians of Reddit, the Ayodhya temple stunt backfired. They were already unhappy due to unemployment. This is due to schemes like Agnipath, reduction in UPSC allotments etc. Instead of tackling that, the government went on vanity projects like the temple, airport, express highway etc. BJP never talked about unemployment, starvation, etc even during the rallies. Instead, every single speech was about Muslims, Mughals and mangalsutra.

And to rub it in their face, a lot of locals were displaced or even made homeless in the process of making the temple. The real benefactors of the real estate deals were Gujjus, not the locals. Even the local priests were not spared - they were replaced by Gujju pandits. Making it worse, the ads for the temple featured our supreme leader in a bigger size than lord Ram himself. People realized the true intentions hidden behind the temple construction.

Another factor was the Dalit treatment. BJP was vocally against reservation, while simultaneously increasing caste privileges, discriminations and violence significantly. To increase those worries, there were cases like Hathras, another one a few days back and numerous unreported ones where a Dalit woman/girl was gang raped, tortured and murdered by UCs. Not only did the government help the criminals escape, in most cases, they decimated the entire families of the victims. Crimes against them were reaching genocidal proportions. Dalits have a significant share of UP’s population. Their collective realization that BJP is going to harm them was a significant driver here.