It’s a standard timeout function without any context. Most likely thing is that it tries to load an ad and if that doesn’t work in these 5 seconds, then the anti adblock popup is displayed. If you don’t use an adblock, the site loads instantly cause the ad is detected. If you use ublock, you see neither the ad nor the popup, so everything that’s left is a 5 seconds timeout.
While it definitely is shady coding, it’s an anti adblock “feature” caused by incompetent design and not an anti Firefox thing.
Exactly, no one knows, but here we are on the 7th article saying Google is slowing down Firefox on purpose. That’s the least likely option by far. That would get them into multiple anti consumer and anti monopoly lawsuits while probably breaching their contract with FF at the same time. Alphabets board of advisors isn’t run by Elon musk, they know pretty much what they can get away with and wouldn’t be stupid enough to try something this big while they are already beeing monitored by the EU.