A generation ago, the picture below looked vastly different. Old network diagrams conjured thoughts of defending a castle. However, the problem for decades has been the fact that people work more outside of their business or castle. As organizations grew, more infrastructure had to be built with servers and software, even though very public passages were made for easy access to proprietary data. The entire monstrosity was difficult to protect. In the event of a disaster, most businesses continued to go bankrupt because little preparation happened outside of the castle.
Today, that whole paradigm has changed with more services outside of your network than inside. If one service is unavailable, other parts of the business may continue to function. When your building is destroyed or communication lines are down, go anywhere there is Internet to resume working. Invert legacy backup processes and keep a copy of data locally. Have just enough equipment to failover on premise. Implement 2-step logon to thwart any hackers. Run business as usual during emergent situations.