Are there succesfull indie developers, who lived from there products, who failed in the long or short term? So for instance went "bankcrupted".

What was the cause of this. The different behaviour of the consumer on the market, wrong updated price and online distribution strategy, bad reviews from the press, pirated/illegal software, no further investment in promotion campaign etc.

Well there are certainly plenty of dead projects that lay in ruin due to neglect or by choice. projects and companies take engery to run. There are plenty of reasons why they end.

However, I think its more often not a single source of failure, but a series of blunders that would lead to the death of an indie company if it wasn't by conscious choice.

All of those reasons you mentioned are certainly factors, but all are manageable if the people running the ship are paying attention.

For almost any stumble, there is a silver lining. it might be a new opertunity that wouldn't have been an option if you would have succeeded in another direction. It might be a lesson learned.

I would imagine all successful indies have a few battle scars, but if we got taken out on the 1st blow, we wouldn't be successful :D