!important means that the rule you add it to will take precedence over other rules that have a higher priority, which is the case here considering that the rule you’re trying to override is added dynamically. So it’s not always need it, but it is in this case.
Here’s an example:
color: #fff !important;
Normally (without !important) .x will be #000 because you’ve set it after #fff. But because the first rule has !important, it will be #fff.
Now regarding your question, I’ll need to see the page you’re referring to. Please note for the future that I, or any other theme/plugin developer, might not have the same test environment as yours so it’s hard to help without seeing.