Settlers might have less of a snowball effect than Monopoly, but it's definitely there. Pretty much any resource-gathering game is going to have it. If your resource numbers get rolled early on, you get to be the first one to build a city or a third settlement. Then your income is higher, so you'll get to the 4th point faster. And so on.

Like another commentor said, the intended fix for this in Settlers is social dynamics: the leader is going to be blocked from the best settling spots, isn't going to get favorable trade deals, and is going to get hammered by the robber. The key strategic gameplay in Settlers is not about profit maximization (that's pretty easy to do), it's about minimizing any appearance that you're a threat until it's too late to do anything about it. If players never collaborate to take down the leader, then early gains can definitely beget later gains.

Even with the social fix, there’s usually one person (sometimes two!) in a four-player game who does nothing wrong but is basically out by the second or third time around the board, just hanging around to help the one or two other non-lead players harass the leader but with no viable path to victory short of an insane run of luck with the dice (or, if you’re me, as soon you realize this has happened to you, you help the leader get ahead faster so you can move on to a better game sooner…)