Why does Capistrano work in one directory and not work in the next one?

Question

Capistrano

Tell.
There is macOS. There is capistrano 2, which sometimes does a good job of deploying a project. But it only works in one directory!
What the heck?
The project is in the ~/work/project/ directory, we go into it, launch the deploy, everything works amazingly.
Rename it to ~/work/superproject/, go in, run the deploy - it doesn't work.
Create ~/work/project2/, go in, run it - it doesn't work.
Temporarily rename ~/work/project/ to ~/work/project252345315/, then temporarily rename ~/work/project2/ to ~/work/project/, run deploy, everything works, then return the previous names...
What do you mean it doesn't work :
- when you run the "cap" command, for some reason, the result
cap: command not found
- when running directly "/Users/user/.rvm/gems/ruby-2.0.0-p0/bin/cap" I see in response

/Users/user/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/2.0.0/rubygems/dependency.rb:296:in `to_specs': Could not find 'capistrano' (>= 0) among 42 total gem(s) (Gem::LoadError)

What's the magic?