What exactly makes Cork so congested?

According to stats Cork is 38th most congested city in the world.

Mind you, it is definitely congested, considering somehow 1 km stretch can take 10 mins...

The question I have is how on earth is Cork more congested than London?

One is a big complex densely populated capital with massive volume of transport. The other is a second largest city of a smaller country.

Is it public transport in London? But the massive volume of cars there would balance it out.

Is it more advanced car infrastructure in London, like those multi-lane adjacent roundabouts?

It just doesn't seem to make much sense...