The shoguns decided to isolate Japan from other nation in the late 1500s because they wanted to discourage revolt against their rule.
At the time, not many people were pleased with shoguns, a military government, and they may have though about an uprising so as to make their living conditions better. However, shoguns had other plans and thus they isolated Japan completely, and to this day, Japan is still probably the most isolated country in the world.
