To understand whether GPU or CPU are more important for video editing, you have to focus on the task itself. Video editing is the process of retrieving, changing and storing data, which requires a lot of processing power. Since CPU is your source of processing power, it is more important than GPU for editing.
The question of GPU or CPU for video editing might come up when deciding where to spend most of your money. If you cannot afford both a top-end graphics card and a processor, it’s always better to opt for a more expensive CPU.