The DUMBS are connected to each other through a worldwide network of tunnels. They used maglev trains traveling at 1000s mph for transportation. It makes sense that they would stockpile food and supplies to prepare for any unforseen circumstances. Their contingency plans included nuclear weapon attacks and real pandemics that would have wiped out half or more of the world population.
As for how it was financed, the Khazarian mafia had money laundering operations that took in trillions over the years such as NASA. The tunnels and DUMBS were a big part of where all that money went.