I had forgotten about the bow thruster, so yes, six engines. The first ship I served in after joining the Navy, an AOR (RFA in RN parlance), had one. They are primarily used for maneuvering into and away from jetties. That said, it was SOP for it to be running and available when entering and leaving harbour. In this instance, I don't know if it would have helped Dali avoid the bridge. It might halve swung the bow away, but she would probably have struck the bridge broadside instead.
While I have no experience with engines like the one in Dali, practically all of the diesels I had experience with were air-started. The Volvo diesels in our RHIBs had electrical starters, but that's the only example I can think of.
If there was a problem with the fuel itself, then sure, it could cause all of the engines to fail. However, I have difficulty believing that it would cause them all to shut down almost simultaneously. Unless, as you suggest, there was a single point of failure, like a single fuel pump supplying all of the engines. You may be correct about fuel, but I'm still leaning towards some sort of major electrical failure. Or, there could be a confluence of events leading to all of the engines failing. Regardless, it's all conjecture right now.