Matt Donnelly Senior Film WriterThe Russo brothers, directors of the all-time top grossing film “Avengers: Endgame,” quietly secured a roughly $50 million cash infusion from Saudi Arabia earlier this year, multiple sources tell Variety.In a deal brokered and closed at the beginning of the pandemic, the Russos received the investment from an undisclosed Saudi bank in exchange for a minority stake in the brothers’ Los Angeles-based production company AGBO.