how to create a nested dict..

[Gribouillis]

it returns the following (ignore the "ansible_" prefix)...

It can't return what you said, because your result is not a python object, neither is your expected output. It makes the question impossible to answer.

If you've read "the zen of python", you know that

Beautiful is better than ugly.

That's why we try to avoid very long and obfuscated list comprehensions. The code would be better with line 8-15 split in several steps.