Based on this excerpt, Disney and Iwerks had a tough time getting their new business off the ground mostly due to

The correct answer is C) the Leatherworkers Union strikes.

Explanation: The excerpt likely discusses the challenges faced by Disney and Iwerks in starting their business, with specific mention of strikes affecting their operations. This indicates that external factors, such as labor disputes or strikes, played a significant role in hindering their progress rather than personal qualities or other unrelated issues. If you need more information or help, feel free to ask!