There are plenty of good, worthwhile non-profits that run ethical operations but there are also some that do not. Just because they have "very thorough and specific bylaws" and publish public financial reports doesn't always mean they are truthful.
Even the Red Cross, long considered by many to be one of the world's most credible nonprofits, was caught in a huge scandal after a 2015 NPR-ProPublica investigation exposed its misuse of funds meant for Haiti relief. The organization had a stellar reputation and published all the required financial disclosures but it took a major investigative journalism operation to uncover the real story.
In Search Of The Red Cross' $500 Million In Haiti Relief
All this is to say things aren't always what they seem. Evangelical super-churches, televangelists and broadcasters have an especially notorious reputation for getting caught in scandals. It's fair to look at these organizations and the executives who run them with a healthy amount of scrutiny. There are certain questions that should be asked of any non-profit and the answers don't always deserve to be accepted at face value.