Didn't that more or less happen? Your phone runs Java (well, maybe not, but most people's do). The SIM card in your phone runs Java. Set-top boxes and TVs run Java. I know a guy who programs washing machines in Java. The servers serving up the pages you read on your phone run Java (or at least the JVM). Most of the current big data software runs on the JVM. About the only applications which aren't Java are desktop apps, and those are kind of a hangover from the, er, 90s.

... and unremarkably, the software on set-top boxes and TVs (and perhaps washing machines--mine's pretty buggy considering the number of inputs and outputs involved) is uniformly terrible, along with most pre-Android Java-based phones. Not to mention the overhead required to run something like Java in an embedded system was until very recently, bad for keeping costs down.

It's notable that the current, much more successful, wave of embedded platforms suitable for DIY work don't run Java.

Is there a general consensus to why Embedded Java and other Java techs like Java Card never took off?

JavaCard _did_ take off. More likely than not the SIM card in your phone runs it, and so does your EMV/NFC bank card (if you have one).

There's a tiny computer inside your iPhone running Java. It really is everywhere.

A great example of the difference between mindshare and marketshare