I almost guarantee you it was an an accident, it would be silly to even attempt to think it wasn't. They were still under power because they need to keep steerage. You can just stop and pull over when you get in a wreck like a car. They have to slow down, slowly. Getting into an collision at sea is bad enough, they didn't want to add running around to that as well.
I have done the Suez Canal and I can assure you that at no time are vessels allowed to pass, come abreast of or get close to one another. Traffic is one way and very closely monitored, with a specific distance mandated between vessels. Speed is closely monitored and transgressor vessels can and are banned from using the canal. Therefor, what we see in this video cannot be a mistake or accident. It could only be caused by an intentional act. Why the captains of both vessels allowed it to happen, I have no idea, for you are correct about that; they are ultimately responsible at all times. Therefor, the following paragraph, as accurate as it is in regards to the physical aspects of the bank effect (which any sensitive sailor can feel in the ICW), cannot be correct. Some how, for some reason, these two pilots and two captains must have knowingly allowed this to happen. Therefor, this is not an accident.
Lastly, to explain why it was an accident. This is a narrow channel, we know this. When you have two deep draft vessels in a narrow channel, hydrodynamics start to really come into play. What happened to the passing vessel is call bank suction. When the depth of water decreases, the stern of the boat starts to shear to the shallow side of the channel. This caused the bow to head to port. It's a fine line and once it starts, and not corrected in a timely manner, can't be stopped with ships this size. These aren't capable at maneuvering vessels, they are made for open ocean and going straight.
But in any case, no professional mariner, not myself, not one, would want to purposely cause a collision or allision or any maritime casualty for that matter. Its license revocation, loss of employment, possible fines, possible criminal charges and jail time, possible loss of life on your hands, why would anyone want that?