What does Koheles 9:1 have to do with the surrounding verses?

Question

The last part of chapter 8 of קהלת and the first part of chapter 9 discuss the fact that good things happen to bad people and bad things to good people. It notes that this is a shame, since it leads people to sin when they don't see sins punished. However, 9:1 is a brief intermission:

כִּי אֶת כָּל זֶה נָתַתִּי אֶל לִבִּי וְלָבוּר אֶת כָּל זֶה אֲשֶׁר הַצַּדִּיקִים וְהַחֲכָמִים וַעֲבָדֵיהֶם בְּיַד הָאֱלֹהִים גַּם אַהֲבָה גַם שִׂנְאָה אֵין יוֹדֵעַ הָאָדָם הַכֹּל לִפְנֵיהֶם

This says that what people do is in God's hands. (I'm using the מצודות for my understanding of קהלת, and my understanding of the verses follows their explanation.)

What does this have to do with the surrounding verses? (Indeed, if anything, it seems to contradict them: if our actions are not our own choice, then our sins would not be reduced by seeing others' sins punished.)

Answer 1

The Metzudos (Dovid) on 9:1 writes:

כי את כל זה. האמור למעלה שמתי אל לבי, ולברר ממנו את כל זה אשר הצדיקים והחכמים עצמם ומעשיהם אשר יעשו הכל המה ביד האלהים, והם אינם שולטים לא בעצמם ולא במעשיהם: גם אהבה. אפילו האהבה שאוהבים את מי, גם השנאה ששונאים את מי, אין האדם יודע מהו הסיבה: הכל לפניהם. כל אלה נגזר מן השמים לפני בואם:

”For all of this” which was said above I placed on my heart, to clarify from it all of this, that the righteous and wise themselves and their actions they do - all of it is from the Hand of G-d, and they don’t rule not over themselves nor over their actions. “Also love” - even the love, that they love someone; “also the hate” that they hate someone, a person doesn’t know the reason. “Everything is before them” - all of these are decreed from Heaven before they came.

In other words: 9:1 makes a great segue between the end of chapter 8 and the beginning of chapter 9, in that the observations at the end of chapter 8 led Shlomo HaMelech to conclude that everything comes from Hashem, the righteous end up like the wicked (9:2), and ultimately to the line you reference in the OP, that people are almost encouraged to sin when they see that it goes unpunished (9:3).