In the tech world I would imagine a scenario where you don't have any professional experience in language X, you've been working only in language Y, but you've done some personal projects in language X and would like a career shift. It's hard to get a senior position without any experience.

Just do a project in language X on a professional, senior level and if you incorporate, you can write you worked for that company on that project.

Probably because they couldn’t get an interview any other way, the reason this person got so far in the process was not because they were qualified for the job, but because the hiring manager liked the fact that they used to work at the same place together. Which is a crappy reason to hire someone.

Sounds like it was for a Sales position. Those types of interviews are easier to BS.

I would guess he lied because he needed a job, and he figured it would have no bearing on his performance on the job.

Industrial espionage or other type of work to gain access to confidential information is one that hasn't been brought up.