For me it was the fact that the first sentence literally just spells out what the line above says. It feels like every other sentence coming from ChatGPT is just a summary of the previous sentence. (Unless it's trying to relativize, then it hits you with the "it's important to remember".)
Eh, I mean it's a very specific flavor of overexplaining and needlessly summarizing, I don't think real ramblings (for lack of a better word) would exhibit this particular writing style purely by chance, even with repeated points.