Usually it is the more aggressive players, but not always. I prefer to play tighter in early levels, because there is a saying that I believe in... "You can't win the tournament in Level One, but you can certainly lose it", if you get knocked out. So I prefer to avoid getting all-in during the early levels.
However, others (including many "good" players) will claim my approach is sub-optimal, and that during the early levels our focus should be on accumulating a big chip stack, even if it means we take the risk of getting knocked out of the tournament.
Years ago, tournaments were mostly "freeze-outs", which is a term that means you only get to enter the tournament one time, and if you lose all your chips, that's it for you, no more attempts. However, in today's modern era, most sites DO allow re-entries, and usually it is UNLIMITED re-entry. This changes strategy quite a bit - not for a tight and cautious player like myself, but for the aggressive gambling type of player. These players are now free to "go for it", take big risks and apply big pressure to players like myself during the early levels by shoving all in with massive overbetting (remember, the pots are smaller when the blinds aren't very big yet so getting all-in during the first few levels can be more difficult to accomplish). If this doesn't win these players a big pot, it certainly does allow them to keep accumulating lots of smaller pots, which still gives them a big chip stack over time. And of course, they are doing it with zero risk, because if they make an error and get knocked out, they just re-enter and keep right on going.
But even tighter players like myself sometimes end up in the top ten spots on the leaderboard in Level One or Two. But that's just the luck of the draw, usually by catching a nice cooler such as set-over-set against someone, or when my flopped set catches a full house on the river when someone else caught the nut flush... for me, it's just luck when it happens, but it does happen sometimes.
So for tight players, a big stack early just means I've gotten a bit lucky. For loose aggressive players, a big stack early just means they are playing their game and doing what they do. LAG players will have a big stack early much more often than a TAG player will, but in the end, it really doesn't matter and is meaningless. I often keep an eye on the leaderboard as the hours pass by in the tournaments I play, and the pattern I always notice is that the players who have big stacks early on, they usually don't make it all the way to the end of the tournament. That's because their aggressive play will usually backfire on them at some point, all it takes is one big mistake in one pot, and their stack is gone, and so are they.
I don't think having a big stack early on really matters very much - most of our chips when we go deep in a tournament comes from the later levels, not from the early ones. So don't worry about players always having big stacks early on - sure, it looks "sexy" when you see the same names always up there at the top, but it really doesn't give them a massive advantage, just a small one. My opinions obv.
