I actually question whether the real story is the fall of Eclipse or the rise of Intellij.
My impression (as someone who used both) is that Intellij IDEA was significantly better than Eclipse (to the extent that I went out of my way to be the sole developer who used it on a team of Eclipse users) but that it was not widely used. Then they decided to release the community edition which enabled people to try it without making a financial commitment. (The "free trials" they had before weren't achieving this -- people knew that any time spent climbing the learning curve would be wasted if they didn't shell out money.) Once people had a chance to see it, they chose Intellij in large numbers because it was a superior product.
For ME, the lesson to take away here is not that Eclipse should have had a more polished project and a more organized organization, but that Intellij was enormously successful because they released an open-source version of their product, and to wonder whether a similar opportunity applies to my own products.
I think it was both: the community edition was certainly a big win and Eclipse got worse. I distinctly remember Eclipse getting horrible before considering other options and finding out about IntelliJ CE.
Did it get horrible, or was it always horrible and the sharp edges finally knawed on you until you looked eleswhere?
I know when I first picked up Eclipse I was blown away by the power(coding in mostly Kate at the time...), some level of rose tinted goggles as first introduction to a proper IDE.
In my experience, Eclipse used to be good and it suddenly became horrible, and it was pretty clear when this happened: around the "Juno" major redesign (which, like I mentioned elsewhere, was both a huge redesign and lacked any kind of serious testing because of budget problems).
It wasn't a gradual, this-is-slightly-becoming-worse affair. It was abrupt. Eclipse really did jump the shark, and you could see the shark flying in mid-air :)
That is certainly accurate in my case: I was aware of Intellij's reputation of superiority, but used Eclipse until the free version came out, and then never looked back.
The rise in usage of the intellij platform also came massively when they decided to make official plug in for some languages, which worked in the ide, but also a "standalone" ide specifically for it.
I know phpstorm saw a gigantic rise in usage, and webstorm too. Right now they're doing it again with their Go ide (which again is intellij with an official go plug in), and their biggest competition is visual studio code, at least from my pov.
They certainly could! That's a basic part of the deal when you offer something as open source.
I wouldn't choose to aid such a project, UNLESS I felt that JetBrains (the company that produces IntelliJ) was being harmful to the community of users.
A perfect example would be OpenOffice. While it was well-run under Sun I thought most effort should go to a single project not to works. Once it turned evil (Oracle) I thought all support should go to LibreOffice.
My impression (as someone who used both) is that Intellij IDEA was significantly better than Eclipse (to the extent that I went out of my way to be the sole developer who used it on a team of Eclipse users) but that it was not widely used. Then they decided to release the community edition which enabled people to try it without making a financial commitment. (The "free trials" they had before weren't achieving this -- people knew that any time spent climbing the learning curve would be wasted if they didn't shell out money.) Once people had a chance to see it, they chose Intellij in large numbers because it was a superior product.
For ME, the lesson to take away here is not that Eclipse should have had a more polished project and a more organized organization, but that Intellij was enormously successful because they released an open-source version of their product, and to wonder whether a similar opportunity applies to my own products.