Since more goods are being shipped to people on a one off basis, there is more demand for all of the resources needed to do this, from boats, to containers, to warehouses.
When you start to see slow-downs in international shipping, there become large incentives to do silly things, like stockpile supply in warehouses, so all of the warehouses fill up, and then all of the container yards fill up, and then all of the container ships have to wait, exacerbating the problem.
On top of all of this, there is a huge shortage of truck drivers, because it sucks to drive a truck for a living.
What can we do about all of this? Expand the number of containers we can store? Seems like an unlikely fix. If you have a clogged pipe, expanding the size of the funnel feeding it doesn't solve the problem.
Why not put a price on the clog itself? If it cost an exponential rate to store containers full of stuff at ports I think the stockpiling would quickly subside, wouldn't it?