Actually there was supporting evidence, but it had nothing to do with electricity or electromagnetic fields. The higher incidence of certain diseases near power lines was caused by poverty. Middle class and wealthy people avoided living near power lines, leaving those areas to poor people, who are more likely to developed diseases related to poor nutrition.
So it was more of a correlation than causation, but most people can't see the difference.
Actually there was supporting evidence, but it had nothing to do with electricity or electromagnetic fields. The higher incidence of certain diseases near power lines was caused by poverty. Middle class and wealthy people avoided living near power lines, leaving those areas to poor people, who are more likely to developed diseases related to poor nutrition.
So it was more of a correlation than causation, but most people can't see the difference.