If Mir was so good and superior they would just keep developing it. Isn't that obvious? If the company who already spent all this dev time aka money on Mir doesn't believe in it, why would anybody else? They were even eating their own dog food and had some major industry pull at their disposal. The answer is they fucked it up.
Not that I care or know a lot about Mir, but do you seriously believe that it was always the best technology that became successful and triumphed over its competitors?
> If Mir was so good and superior they would just keep developing it. Isn't that obvious?
No, that's an arbitrary conclusion you've made. There are multiple reasons why a project might be killed, even if it's a good one. Canonical killed Ubuntu Touch but now it's gaining traction again because we have things like the Librem5 and PinePhone. Premature if you ask me but it makes sense as a business decision.
If we look across industry, would you say killing Google Reader was because it was inferior to others? I wouldn't.