[caspper69]

Had we had better process isolation in the mid-90s, I assume web application development would mostly be Java apps, with a mini-vm for each one (sort of a qubes like environment).

We just couldn't keeps apps' hands out of the cookie jar back then.

[immibis]

Java tried to, and mostly successfully did, run trusted and untrusted code in the same VM. Your applet code ran in the same VM as all the code for managing applets. However, holes were frequent enough that they abandoned the whole idea. (Instead of sandboxing the VM as a whole? Why?)

[lmz]

The whole applet thing was already slow enough then without scrutinizing every syscall it makes.

[vessenes]

Well we had flash. It wasn't great. Or it wasn't great enough to keep around without a major browser or OS provider pushing it.

I will remind you that Swing sucked, hard in the 1990s. And HTML was pretty easy to write.