>>512179670 (OP)The "mandate" is called like that as it was mandated by the league of nations, it was something given to Britain to be its stewardt. The point of the mandate was to develop and prepare the territory for its eventual independence, not to engineer hostilities and to breakl it half and scurry away in the night.
Palestine got broken up for the same reason germany, korea, vietnam and india got broken up. Plain desire to keep eurasia in a state of chaos.
Same reason there was an attempt to break China in two which mildly succeeded as it lead to the creation of Taiwan, but originally it was going to be half of China.