"After publishing the book, Kalergi received help from Baron Louis de Rothschild who put him in touch with one of his friends, banker Max Warburg. Warburg then supported Kalergi with considerable funds to help form his European movement."

Some good articles on the kalergi plan"
https://themillenniumreport.com/2018/01/kalergi-plan-the-covert-scheme-to-destroy-europe-from-within/
https://englishnews.org/2020/01/31/the-kalergi-plan/
http://historyreviewed.best/index.php/the-kalergi-plan-for-white-genocide-was-backed-by-famous-powerful-jews/