When event freshness is enabled on your re-ranked index, more weight is given to items with more recent events (clicks or conversion) and so these items are given a higher attractiveness score and ranked higher, despite potentially having fewer events.
You can read more on how Attractiveness Score is calculated here: https://support.algolia.com/hc/en-us/articles/27094885406353-What-determines-Attractiveness-Score-in-DRR