Economics killed the A380. Plain and simple.
In the airline industry there is a thing called the America West lesson. In the '90s America West bought 3 747s. On paper the 747 was the most economical airliner at the time, If you filled it up. If you don't it burns though cash faster than any other airliner. The fixed costs are so high. The 3 747's did not last long.
The A380 has 4 engines and quad redundancy on all the systems. It equates to 2 times the maintenace than a 777 or A330 and twice the fuel burn. Yes it carries a lot of people, but the cost to buy and opperate are huge. The flexibility that 2 A330's gives an airline is also very important.
The 787 and the 737-800/900 changed the way airlines operate. They had the range and the lower operating cost to open up city pairs that previously could only be connected through hubs.
Airbus answered with the 320NEO and the A350.
These aircraft greatly diminished the cost advantage to large hubs.
There is a reason all new airliners have 2 engines. Cost.
The A340 failed and the A380 is in its death throws, as is the 747.