From a Google search on olive tree pruning, see especially the 2nd paragraph:
Origins
It seems that the often gnarled and gray branches and trunks of the fairly small olive tree were first cultivated for their olives about six thousand years ago in areas of the Middle East. They have been cultivated on the island of Cyprus for four thousand years or so. This slow growing, but long living evergreen takes about ten years to grow to maturity, but after that it yields olives for perhaps hundreds of years.
For maximum production the tree needs stringent pruning every ten years or so, cutting right back to the main branches. This rejuvenates the tree and crops can be expected to increase to full capacity within three years.
In North Cyprus, as in other Mediterranean countries the olive tree can be seen everywhere, in the wild and under cultivation. Usually favouring well drained sunny hillsides, olive trees can nevertheless thrive in backyards and flat plain lands.
The nurture and care of olive trees is a matter of some skill. Although olive trees can live and produce olives for hundreds of years, they do need skillful pruning and without attention they can soon die off. This has been the case in North Cyprus, but now that young trees planted and have started to produce, growers are hoping once again North Cyprus region will be a serious Mediterranean producer. Some estimates suggest that there are about 800 million olive trees under cultivation around the world, and nearly all of them are in the Mediterranean countries
One last thought. I wonder if the settlers figured the palis weren't going to take care of the trees and wouldn't go to all the work of pruning them? And the settlers figured they would be back in after a few years and wanted to have healthy trees to come back too?