Probably internet speed plays a big factor.
It's not an internet speed issue. The bridge doesn't have much memory, so it has to be loaded in small pieces at a time. That's probably causing a lot of back-and-forth transactions causing the servers to get bogged down as the load increases. It's also a relatively large update compared to previous ones, which doesn't help.
It's kind of like how copying one large computer file is a lot faster than a copying a bunch of tiny ones.