Dude. We know nothing about Eostre, and barely know the highlights of the retconned holiday around it.

If future archaeologists can figure anything out, I’ll be convinced of their greater intellect.

Also, “religious whackadoos” is a good guess for why people do anything weird, these days (eg “Tennesseans vote to kill bills and laws that help them all” and similar weirdness), so I think that’s a good initial strategy.