How on earth is CSR actually calculated?

Seriously, I just don't understand how CSR is calculated after each match. Last night I played a match and we were all ranked Platinum 1. My results are the first picture (Diamond career rank). I had the highest overall score, kills (and deaths). Compare that to the second picture (the Hero). I have a decently higher overall score and did better in each category except secures (only by 1) and assists (by 5). Similar results with the 3rd picture (Platinum General) but it was a bit closer between us.

I only got +7 whereas the Hero got +9 and the General +8. I know it's not a big difference and I shouldn't complain that much, but I'm just genuinely confused why they got more CSR than I did. The same thing happens when losing CSR too. Despite doing the best on my team overall, I still lose more CSR than the others, even when we're the same rank.

The only thing I can think of is that it goes SOLELY off of KDA. My KD above is 1.05 and my KDA is 1.32. The Hero's KD was 1.06 but their KDA was 1.71. Similar for the General. Why ignore the objective though?

Can anybody explain it to me? Thanks!