Would interesting to hear about J2ME gold rush. Any success (or fail) stories?

It was really a euro thing. Think the whole Jamba/Jamster ecosystem (Crazy Frog) and the explosion that occurred with premium SMS and ringtones.

It was all about selling into carriers associated with that, and that was a recipe for pain. I don't believe anyone made a killing in J2ME directly (Gameloft gave the impression of making most money, not entirely undeservedly), and many absolutely struggled, but it did provide the crucible for a lot of what came later.

One of the more curious incidents that stayed with me related to the game "Fatal Force" which had a 64kb build that was incredibly tight. We were mystified to discover a Chinese pirate was distributing a Chinese build of the game, still within 64kb limits. He had decompiled it, reverse engineered it, added more compression so he could fit in localized assets, and released it. The last I heard on the subject there was an effort to pay him for it.

The other was when a game of a game show was advertised in Germany, during the game show, it would generate such a traffic spike that the servers selling the game got knocked out, leading to requiring outsourcing that function to a more scalable competitor, a lesson that was not forgotten for the next company.

Corecursive had an interesting episode with a good story. https://corecursive.com/mobile-ui-with-shai-almog/