The correct answer to this open question is the following.
Although there are no options attached or further references, we can say the following.
Frank Crow's attitude toward building the dam was decisive. He was determined to build and end Hoover Dam at all costs. The problem did this lead was that he had many inexperienced workers and limited time to built the gigantic project. This produces many challenges and problems to the degree that he faced some worker's protests and the threat of going on strike. Workers were against a pay cut and also demanded better working conditions under that risky endeavor.
Workers indeed went on strike but Frank Crowe firmly stood and resisted the strike. He was supported by his contractors and he placed an ultimatum for workers to get back to work or leave the construction definitely.
Everybody knows how the story ended. People said that Crowe was a firm leader that knew how to manage problems and convince his workers to finish the challenging project.
