Why did Java fail as an internet client platform?

The reason I reflect on it now is that Flex has gained a lot of traction and I am using it now for a project. It's pretty much the same concept as a Java applet but Adobe has done so much better than Sun. First, the client penetration of the Flash Runtime is higher than the Java runtime. Second, if you do need to install it, the entire runtime is 1.5MB. That is less than the Java runtime back in the year 2000!