Why would three airlines offer an identical long-haul connection within minutes of each other? [duplicate]

There can be many reasons:

1. There are no airport slots available which match both departure and arrival airports and the time between.

2. Airplane is used further to an another destination at arrival (i.e. it has only short layover in Seoul) or airplane is comming from somewhere (i.e. it has short layover in frankfurt and then fly to soul).

3. There is high demand between both cities.

4. Planing for such long-haul flights is made months or even years ago by airlines and it is not easy to change these planes suddenly while keep in mind that airlines keep such plans very secret until they are rolled out.

5. @Nean Der Thal - Out of personal experience, long haul flights arriving at mid-day is the best jet-lag friendly flights. Perhaps that why airlines choose these timings. Usually people tend to book a flight arriving a day earlier when attending businesses after a long haul flights. The airlines I work for has almost all of its long haul flights arriving at mid-day.