Cranberries evolved so they wouldn't be eaten.
Most fruits want to be eaten so that birds disperse the seeds.
Their preferred method of dispersal was dropping into flowing water, so that they could find somewhere nice to grow near water.
The astringent taste was to stop birds eating them. They became buoyant in water to help them float down stream.
Humans appeared and loved that dry flavour.
Became one of the most eaten fruits on the planet.
Humans even harvest them by flooding and using their own buoyancy against them.
They will get their revenge.