Very very much doubt it’s for the money;
AI
Charles Spencer, the 9th Earl Spencer, has an estimated net worth in the range of £150 million to £200 million.
(https://hub.stellantis.com/article/how-earl-spencer-s-2020-fortune-reveals-britain-s-aristocracy-s-hidden-wealth),
(https://www.nine.com.au/lifestyle/royals/princess-dianas-net-worth-a-breakdown-of-the-peoples-princesss-wealth-20200801-p5q78u.html)
Sources of Income
Althorp Estate: The cornerstone of his wealth is the historic Althorp Estate, a 12,000 to 13,500-acre property in Northants.
The estate generates revenue through agriculture, tourism, public summer exhibitions, and hosting.
Media and Broadcasting:
Income as an author, journalist, and broadcaster, including writing several historical books, public speaking, and podcast hosting. (https://www.youtube.com/watch?v=8Wevr9R4jQA)
Investments and Real Estate: Diversified asset management, financial investments, and valuable holdings such as art and porcelain collections.