also danny.... sorry for the inc wall of text but this. (found this on dota2 reddit in response to the topic of snowballing games in dota vs snowballing in lol)
Comebacks are easier in Dota for a number of reasons. First, spells only scale with levels in Dota. If an enemy ganker, let's say Lina, is keeping your hard carry down by bursting them every time they come to lane, you will fall far behind. But once Lina hits level 16, she's not getting any stronger. She can buy a bunch of int items and have more disables but she doesn't do that much more damage. Meanwhile if your carry manages to get a couple items they can not only survive Lina's spells, but kill her and start coming back. Compare to League, where if an enemy kills you they come back and keep killing you with better spells and attacks, because everything scales.
On the other side of the coin this can work in favour of those early-game heroes. If the enemy Morphling gets big off your Lich/Enigma there is still hope. Abilities like Black Hole, Chain Frost, Ravage, etc can still have a big impact even when the enemy carry has been fed a bit. They will always retain some usefulness, so if you use those abilities well you can get things back under control and in your favour.
Another thing that changes how Dota snowballs is the cost efficiency of items. Compare an Ironwood Branch to an Ultimate Orb. 10 Branches would give you the stats of an Orb for a quarter of the price. The reason you pay so much for the Orb is to save inventory space and the hope that you can build it into a bigger item. So if someone gets fed and they go "yes, I can get my Ultimate Orb now!" it's not so bad. You can buy a cheap 530 gold item like a Bracer and be almost on par with them for the next little while. Even though you died, you're on equal ground until they get a big item. Components aren't that valuable.
However in League, expensive items are more cost effective than less efficient items. A BF Sword gives more ad per gold than a Pickaxe. In League a more expensive item is always better, which means someone who gets a couple of kills in lane is likely to snowball because their gold can be spent more efficiently. When someone in League gets a couple of kills and goes "yes, I can get my NLR now!" and you're still sitting on 900 gold it is a very hard situation to get out of. A Blasting Wand will be weaker than their purchase because more expensive=more power in League. There is no momentary weak period in their build. Add to that the fact that there are barely any cheap "I need some power RIGHT NOW" items in League and things will spiral out of control for a losing team.