Not sure how you built your minimal example, but current versions of Java will allow you to produce much smaller native bundles using jlink. Steve Perkins did a nice little writeup with an example repo at https://github.com/steve-perkins/jlink-demo.
This is only the case if you bundle the JVM with your application. Without the JVM you can write a simple application without exceeding the .jar file size of 1 MB.
I should have been more explicit; this is the default in memory footprint of a simple hello world app. I didn't really try to reduce the heap or stack of the JVM, I'm sure that would help.
Oh I think this is a misunderstanding. I thought you were talking about the binary file size which is very big for electron apps since they ship a full-blown browser. It is possible that JavaFX apps also use a lot of memory (RAM) but I was referring to the file size of the .jar file of a JavaFX app.