Nepal is a mountainous country. To state the obvious it is prone to earthquakes, followed by mudslides etc. I am not surprised that no new building has started yet.
That is because, first they need to clear mudslips and road damage on the few roads that go to the many remote regions affected by the earth quakes. Then they have to rebuild and repair the roads, not easy, when a hillside has disappeared. It needs to be built from scratch on a new route that they hope will be safe and not prone to mudslides. The same applies to restoring electricity and telecommunications.
Villages have completely dissappeared under earth and mud and need to be rebuilt from scratch, on new sites, with new foundations etc etc. then there are problems of logistics, getting materials to villages and and so on and so on.
Many temporary homes were provided in the immediate aftermath of the earthquake, and while obviously one wants progress and rebuilding to go ahead as fast as possible, there is no point in hurriedly erecting unsuitably designed houses, in dangerous locations, where they may be washed away in the next flood season, just to look good to donors.