Final answer:
The industrial moguls and financial sector backed William McKinley's campaign financially to ensure William Jennings Bryan would not win the presidency due to their preference for McKinley's economic policies.
Step-by-step explanation:
To influence the election and prevent William Jennings Bryan from winning, the titans of industry and those with vested interests decided they needed to fund McKinley's campaign. Considering the economic policies Bryan advocated, like the coinage of silver, alarmed the financial sector, they preferred the stability and probusiness approach of McKinley who championed the gold standard. Thus, they used their wealth to contribute generously to McKinley's presidential efforts, ensuring he had ample resources for his 'front porch' campaign strategy which stood in contrast to Bryan's vigorous stumping across the country.