Answer:
In the past, Nepal tried to divide is nation into several smaller regions. Each regions were given the autonomy to rule itself like a smaller nations. But as it turned out, the system did not work very well.
Some regions were heavily underdeveloped compared to the others. On top of that, these regions often involved in a conflict with one another. Causing internal damage within Nepal and made it a vulnerable target for other countries.
This is why federal system felt as a necessary option for Nepal. By centralizing the government and forcing all regions to follow its regulation, Nepal hoped to eliminate disparities between regions, solve the internal conflicts , and ensure that all parts of Nepal were proportionally developed.