If you just funnel reddit users onto Lemmy, you’re just going to get a shittier version of Reddit. You’ll be selecting for people who are tired of, can’t use, or rejected from reddit, but didn’t make the move on their own. That will result in growth, but at the cost of quality. Specifically reaching out to reddit users sends the message that you just want to be reddit for people who can’t or won’t use reddit anymore.
Expansion should come naturally. As Lemmy grows and improves, new users will naturally gravitate over, but because it wasn’t some sudden influx of reddit users they’ll be less inclined to just bring Reddit’s culture with them.