...but fault lies at the tower personel who let the plane leave. If we can wait for 4h, what is the harm to have the connecting flight delay for 1-2h so that more people can get on it right...
You lose me right here. And you seem to not understand how this all works. Tower personnel have the aircraft assigned a departure slot, which it's up to the airline pilot/dispatch center to make. This was an MU decision.
As to harm, there is harm to all the other people who have to wait around. The needs of the others outweigh the needs of the 50. A delay ripples throughout the system with aircraft not being where they are supposed to be. Finally, the crew, if they delayed per your desires, may have faced "timing out" which would have set everybody back to square one waiting for a fresh crew to be assigned.
It's just bad luck, sooner or later happens to everybody who travels enough. I'm not sure if you'll have any luck getting anything more out of MU or anybody else.
On a general note: with connections like this, via coastal cities in China during the summer, always prepare for a lengthy connection longer than you might imagine due to bad weather. Make your destination plans accordingly flexible.