It's up to the members of a union to take sufficient interest in it that there are appropriate and effective governance structures in place - in the same way that it's up to the shareholders of a business to do the same.
Organizations of any kind have someone they're supposed to serve - from your neighborhood bowls club to a fortune 500 company.
Organizational (corporate) governance is how you make sure the organization is operating for the benefit of its intended recipients.
Some organizations do governance well. Some do it badly. When the owners (shareholders, members etc) take their eye off the ball over time that organization will skew towards badly.
I don't think this is a controversial statement at all, even when applied to workers' unions.
It's up to the members of a union to take sufficient interest in it that there are appropriate and effective governance structures in place - in the same way that it's up to the shareholders of a business to do the same.