A few months ago, I got an interview for a job but didn't get the offer. The same exact title job got posted recently and I applied and got rejected. Reasons why?

Like the title says, I applied for and got an interview for an out-of-college position in my city. I felt the interview went really well, reasons for being: the interview felt more like a conversation, I had answers for all questions, the interviewers (three of them) told me I was "perfect for the job," and it took them a while to get back to me, telling me it was a difficult decision and they ultimately went with another candidate.

My current job is lacking work and I may possibly be laid off. So, going on the computer, I saw they posted the exact position and so I applied.

I made sure to mention that I interviewed before with them in my cover letter (was this a mistake?) and gave the reason for leaving my current job (was this also a mistake?). I updated my resume with my ~6 months of experience and made sure it was polished.

So, what are the reasons why my application was rejected outright? Was it a bad idea mentioning my previous interview or current job circumstances?

For reference, I am a recently-graudated Mechanical Engineer in a major US city.

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