The difference is in what motivates getting to the other end of that transition bump and how big the bump is. That’s why it took till past 2.7’s EOL to actually get people on to 3 in a big way because they’d drag their feet if they don’t see a big enough change.

Compiled languages have it easier because they don’t need to mix source between dependencies, they just have to be ABI compatible.

The Python community consisted of tons of developers including very wealthy companies. At what point in the last few years would you even say they became “rich enough” to do the migration? Because people are STILL talking about trying to fork 2.7 into a 2.8.

I also disagree with your assertion that 3.x releases have significant breaking changes. Could you point to any specific major breaking changes between 3.x releases?

2 to 3 didn’t break syntax for most code either. It largely cleaned house on sensible API defaults.

I think it’s a larger problem with interpreted languages where all the source has to be in a single version. In that case I cant think of much.