It's not stated that her Dad owned a construction company, only that Neil worked in construction and was hired to build a hotel for this "flithy rich" guy.
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Even if her Dad did own a construction company, most of the big ones are owned by millionaires, or they're owned by capital or investment firms that are owned by billionaires. Most millionaires and billionaires have their fingers in many different pies and own companies/run businesses in different sectors, or at least have investments and stock tied up in different areas.
So it's not impossible to believe that 2 rich men founded a college and that their families have gone on to become incredibly wealthy and have business interests in a few different areas, including owning and operating hotels. It would be like if the great-grandfathers of the Walton and Pritzker families had founded a college together.