Composition of relic
Nuclear power plants were decrepit, outdated, and inefficient.
Factors that led us to abandon this object:
Nuclear power plants were cost-prohibitive, inefficient, and the waste produced was toxic for a million years or more.
Obstacles in the way of this relic being abandoned:
Politicians who were greedy, and power producers who cared more for their profit margin than for the environment were the major roadblocks to eliminating these plants.
Strategies we used to overcome those obstacles:
We stopped subsidizing nuclear power, and forced companies to to come up with ways to safely dispose of waste, thus bankrupting them.