Material Design is mostly linked to Matias Duarte. I would ask you to take a look at his history instead of just asserting that it's just ad industry professionals.
I strongly disagree that this is design agency BS!
Please watch the video where they introduced material design (way back at some I/O) to see what all those words mean.
I hate MD and this video helped me to understand why I hate it: they are trying to do judge by analogy, which causes «analogy driven design», where you should understand analogy to understand what you see. I newer saw real objects to behave like their imaginary «real objects». It looks like they are just getting money for something that nobody knows how to do properly, so they are doing something and arguing correctness of their work with self-made arguments. IMHO, if they will be hired to do an animation film, they will be fired pretty quickly for their «material design», because it looks false.
Its occurrence here indicates that Google hires expensive design professionals with impressive ad industry résumés, I guess.