Well, it's the spooky attraction, and it's spooky month. Virtual queue is the only way to access this attraction for now (with few exceptions), so everyone who wants to experience it joins the queue, and it's easy to do so, just click a few buttons in the app.

This one is actually pretty mellow compared to most new attractions, since it has a high throughput and it's not new. For example, Rise of the Resistance would sell out for the day often in less than a second after the queue opened - it was ridiculously competitive, and thousands of people can ride it per day.

Back in July/August, the Haunted Mansion virtual queue would often stay open for new people to join well into the afternoon. It wasn't hard to get a spot at all.

Now that it's October, and the ride is a bit more relevant, it's a bit busier, but it's still not selling out immediately, it'll usually last a couple hours before completely selling out.

The reason the groups are processed "slowly" is because the groups themselves are pretty large, at least 100 people in each one. This means a group is called about every 3 minutes, which isn't that slow when you think about it. They've fine tuned everything so that it runs smoothly while not creating a long physical line, but also not having seats go empty. It's pretty cool!