It's a design trend, and the digital design space is relatively small and strongly-connected. Many companies use the same set of design shops, or employ designe

It's a design trend, and the digital design space is relatively small and strongly-connected. Many companies use the same set of design shops, or employ designers who look up to or learned from those shops. It's analogous to how engineers across the english-speaking world simultaneously began using Docker or Hadoop or whatever. "Network effects".