I quite like Penrose-Hameroff's theory https://www.youtube.com/watch?v=xGbgDf4HCHU

My best summary of it: consciousness is primal, every bit of matter has perspective, every interaction has experience, the body you're 'occupying' is having a particularly complex and long-lived experience.

As for your question of why this one, well, someone's got to be having this one. As for why not another, there's no saying 'you' won't have another 'after' this experience ends, but if 'you' had them in a perfectly undifferentiated way that'd be a different experience again, and as stated, someone's got to be having this one.