it's the slowing down of the critical part of your brain and more towards the creative part,,,,,,,,,, at night (or at least once you've hit the point where your brain feels like it should start preparing to sleep) critical thinking slows down, which makes it easier for creativity (though not necessarily productivity) as a result of much less nigh-immediate criticism from your brain moderating your thoughts. this doesn't mean productivity is directly increased, rather bc you aren't constantly evaluating & criticising your work's quality & quantity at each moment, you're much less hesitant to do stuff even if it's stupid or in the morning you'll think it's of bad quality, therefore productivity is less hindered!! it's the reason why if you can more easily write something like an essay or story or poem at night than day!!!! fun fact, this is also the reason why you aren't supposed to immediately trust anything you think about yourself (& other people) past like 8pm!!!! your critical thinking cannot immediately catch & assess your emotional responses, bad ideas and instinctual assumptions about stuff once it gets late, so you're more likely to catastrophize (or even underreact), do stupid things and feel like you hate everyone/yourself (or everyone hates you)!!!!! it's really interesting!!!!!
and once again i have yapped!!! apologies it took so long!!!!