Brant Rubin started a hedge fund last year only to find it wasn’t the easy path to riches it used to be. He’d quit his job buying into European internet companies for London’s Luxor Capital in 2017 to set up his own shop and raised almost $50 million from family, friends and a couple of former clients. Then, reality struck. The fundraising didn’t cover his overhead and his corner of the market was falling out of favor with the forces he had to answer to: potential customers and European financial watchdogs imposing onerous new rules.