I feel like Lermontov's approach leaves the reader fairly free to interpret it as they like. However, this being said, I'd like to guess at the author's intentions in ending the novel in a way that may suggest predestination. This choice was likely made as a way to remove blame from Pechorin for all the things he's done. Reflecting on the lives he ruined during the course of the short work the reader could easily conclude he is an awful person. By suggesting that the narrative operates in a world where fate may exists, the fault is shifted from Pechorin to a (cruel) higher power. I do not know whether or not I feel this is fair.