Germanolic

I was translating "I did not forget to write in my diary today" in German and though of the sentence "Ich habe heute nicht in mein Tagebuch zu schreiben vergessen", but in the deepL translator, it says "Ich habe nicht vergessen, heute in mein Tagebuch zu schreiben" Why is "I have not forgotten" followed with a comma and "today in my diary to write" written later on and it is not written all together with vergessen at the end like my previous sentence?