I think that was just a matter of fortunate timing. The other Reddit migrations were due to toxic subs being banned, so the worst parts of Reddit migrated to whatever platforms were being discussed at the time, which happened to be mainly Voat.

The July 1st exodus was due to the Reddit API being paywalled at extortionate rates to crush third-party apps, which affected normal users - particularly long-time contributors and the tech-savvy. Lemmy discussion was picking up steam at the time, so that's where a lot of these users went.

If the timings were reversed and Lemmy got the worst users Reddit had to offer Lemmy probably would have handled it much better than Voat did (especially since the devs would loathe the new users), but I'd imagine a split forming between instances, with right-wing instances being defederated and creating their own bubbles of toxicity.