what was the turning point where the site became so puritan anyway
My best guess is when Trump came into the picture.
Before Trump showed up into the picture, Kiwi Farms leaned more towards the center-left compared to the 'No Fun Allowed' zone we see now.
It was an edgelord's platform but it was an edgelord's platform that used to lean a bit more Left back in the day.
When Trump came into the picture, suddenly some of the Kiwis thought America was finally going to get its own version of Fransisco Franco or Adolf Hitler simply because Trump said illegal immigration has to end.
While Trump is not wrong about illegal immigration being an issue in America, a lot of Rightoids misinterpreted his rhetoric where they thought Trump was going to kick out the Jews and massacre minorities but they failed to realize that Trump is at best a moderate 1990's styled Democrat.
Trump Derangement Syndrome comes in a lot of flavors and while the most common flavor of TDS is the people that A-Log Trump for just existing, TDS comes in a more subtle variety too where those that dickride Trump and the MAGA movement (Trump Enslavement Syndrome) think Trump is going to save the white race and turn America into a white ethnostate where a lot of people who didn't support Trump in the first place would come to support him over a flawed belief that Trump is going to save the white race (which is absurd because while Trump is anti-illegal immigration, this doesn't mean he is pro-white and he has deported plenty of white illegal immigrants back to whatever European or Anglo country they came from).
If Trump is the savior of the white race in America then he is doing a pretty poor job at it because he is also heavily cracking down on white illegal immigrants too (he's not just deporting the blacks and browns that are staying in America illegally). A real white supremacist would probably let White Europeans and whites from the Anglo nations stay in America despite being illegal immigrants to help rebuild the white race (much like how Hitler gave Nazi citizenship to those of Germanic decent that lived outside of the Third Reich) but Trump is deporting plenty of whites that are not American citizens and not legal residents which means he has no desire to strengthen the white race as his immigration policies doesn't really favor whites living outside of America either.
Basically before Trump, Kiwi Farms was an edgelord forum that leaned more towards the moderate Left but Kiwi Farms after Trump came into the picture has caused Green Reddit to think they could be wearing military uniforms by Hugo Boss someday. There are some Kiwis that know Trump Enslavement Symdrome is cringe but a lot of Kiwis still think they may someday get to throw people they don't like in the gas chambers when that will never be the case, period.