In the mid Eighties DC rebooted it's universe after a big event called "Crisis on Infinate Earths". After it was finished all the big comics started over again with issue #1 & they more or less ignored most of what had come before and started telling stories with the assumption that everyone was just starting out.
After Crisis, Superman was still superpowerful but could no longer move planets, and Lex Luthor was an evil and corrupt buisnessmen rather than a scientist. When he needed evil gear, he had his people make it.
After many years of antagonizing the big blue, he ran for office. With all his wealth, power, and contacts, he won.