Columbus Day (or Indigenous Peoples' Day, as some might call it now) is kind of a sneaky holiday at Disney World. It's only one day, and not multiple days or an entire week, so most people think it won't be crowded. But this is often incorrect - Columbus Day usually spikes crowds leading to long lines and frustration among guests.
One thought I had was that Mickey's Not So Scary Halloween Party had an impact on Magic Kingdom crowd levels as it often does. However, in this particular case, I don't think it matters much. For one, if we're looking at crowd levels across all parks, this should simply mean that the same amount of people are dispersed to the other parks on those nights, so the overall levels should be similar. And second, we're at the time of year where the Halloween parties are more prevalent - this past week alone, four out of the seven days of the week, that park closed early for the party. This is the same as last year, including the same days of the week.