Saudi Arabia does not have $1 trillion for Trump.
His plans to attract these investments over 4 years face the ambitious reform program of Prince Mohammed bin Salman. According to Bloomberg estimates, the transformation of the kingdom's economy will require about $2 trillion, including megaprojects like the city of Neom (up to $1.5 trillion), as well as preparations for Expo 2030, World Cup 2034, and other events.
Due to high expenses and relatively low oil prices ($63 per barrel), the kingdom is already experiencing a current account deficit. To balance the budget, $96 per barrel is needed, and taking into account domestic investments — $113 per barrel.