my understanding was that java was originally envisioned as a runtime for iot. i remember reading a lot about how they were expecting it to land in cell phones, set top boxes and other internet connected devices.

they started with applets in the browser. at the time javascript was incredibly immature and used mostly for client side validation of form fields; but was hated by users and developers alike because browser support was inconsistent leading to spaghetti code and bad ux.

java applets were also frowned upon. the jvm was quite heavyweight and would struggle to start up on the pcs of the time. the immaturity of the technology made the uis sluggish and fragile.

i don't think anyone expected it at first, but using java in web backends became very popular. i suspect this was because performance was reasonable once a server was warmed up and it was sort of turning into an ecosystem that a lot of money was being poured into. the microsoft ecosystem for internet stuff at the time was buggy and terrible, with its "systems built to run internally on corporate networks" lineage showing. on the backend, iis was known to be insecure and hard to code for and on the front end, nobody wanted to aid microsoft lock-in with client side vbscribt and activex.

the geeks wanted internet native unix based servers and the well trod options there were java, perl and php (or bespoke options built on them). nobody wanted to do strings in c/c++, further pushing towards high level languages of which java could be a performant one for heavy workloads.

ironically, the java iot dream was eventually realized by google with android. even more ironically, it's probably the most complicating and complained about part of the platform.