Good article that goes into the history of Web Assembly including parallels to ActiveX and applets and how things are different this time:
WebAssembly is arguably a more direct path towards achieving the idealistic goal of “write once, run anywhere” than Java/JVM ever was. This is thanks to the open nature of the whole stack, potential developer mind share (spanning big and diverse set of languages and ecosystems), and direct involvement of browser vendors such as Apple, Google, Mozilla and Microsoft. This is the opposite to the fractured ecosystem we saw in the 90s and 00s, where every vendor had their own special plugin and forced you to use a specific programming language as a gatekeeping measure.
The fact that the vast majority of consumer computing devices…have a universal virtual machine that can be targeted by virtually any programming language is still fascinating to me.