I remember years ago when Breaking Bad was the big thing everybody watched I watched every single episode the moment it came put, and I absolutely loved having to wait a week to be able to see the next one. Why? I remember this episode that ended with a cliffhanger in the middle of a shooting. Immediately after the episode ended fans started to create theories with screenshots of a top down view with arrows pointing at who was shooting at who and stuff like that. Other people commented about how the wind would slightly change the direction of the bullets, so person A might actually hit person C in stead of B etc. Those moments of speculations added a lot to my excitement to watch the next episode, if only to find out if my theories, or the ones I read about online, were true. The same thing happened years later with the first season of Westworld, where 3 or 4 episodes in I thought I figured out pretty much every big twist of the show, so that added a lot to my excitement for the next episode once again. I wanted to see if I was right, and I had a whole week to think about possible theories of stuff that could happen in the next episode. Now compare that to a TV series on Netflix, where you can just watch the whole season at once. A lot of that speculating with fans on message boards, and thinking up theories, would just disappear. You can just watch the next episode and find out what happens. I honestly am a lot less hyped, and cliffhangers really don't do anything for me, when I can just press a button and watch the next episode.
Now compare this to, let's say the From x George R. R. Martin leak. That information leaked and we as a community immediately started speculating. A lot of us didn't believe it, but others came up with theories about how it could work. It was a really interesting and fun time for me and I really loved reading all of the posts in the thread and it made me super excited to find out if the game was actually real or not. Then a couple of days ago the key art leaked and it was pretty much confirmed to be real, and my excitement shot through the roof. Not only was the game real, but we were going to see a trailer in a couple of days! Then today the trailer dropped and I loved it. Of course, I don't know how I would've reacted if I didn't know that it existed at all, but knowing myself I would probably be confused at first, and a bit mad/disappointed after that all we got was a CGI trailer with no date or even release window. But now, I had all this time to warm up to the idea, get excited to maybe get an early look at the game at E3, speculate with you guys about if the game was real or not etc. All that stuff really added to the experience for me, where if I didn't know anything of the game, I probably wouldn't be as hyped as I am now, because I would've missed all those weeks/months of pre-trailer buildup.
This could just be me, and I totally get that From would've wanted today to be the first the world heard about the game, but I just wanna give some insight about how to the consumer, or at least me, leaks like this aren't always a bad thing. They can create hype, they can create a fanbase before it's even announced, they can warm people up to a strange concept (for example Mario x Rabbids) and so on. I totally get that they usually are marketing disasters, especially the really early leaks, heck, I wouldn't want any of my art to leak before it's finished, but in certain instances, for certain people, there are upsides to leaks like this.
For example the upcoming Nintendo Direct. Not knowing if Animal Crossing will be there is killing me. I haven't had an AC on the Wii U, and I've been playing New Leaf for 6 years or so now, a new game is long overdue. But all Nintendo gives us is a vague 2019 window, and 6 months in they haven't shown a single thing of the actual game. I'd rather have "sorry, no Animal Crossing this Direct" than not knowing if it's going to be there. I would've loved it if last year when they announced it, they would've said "we will show it at E3", in stead of staying quiet like this. In this instance, a leak would really help calm a fan base down that has been waiting on information on a game for years. Just knowing if you're going to see something you really want to see is better than not knowing if it's going to be there. At least it is for me. Then again, Iam someone who fucking hates Christmas presents. I'd rather know a month early what I'm going to get, so I can spend the entire month building up excitement until the moment I can finally have it, than knowing I'm getting 'something' and having to live a month with an uncertain feeling if it's even something I want, or if it's something I may already have etc. Maybe that's because of my autism, haha, but yeah... This post has been going on for way too long now, haha, butI just wanted to give some examples of how leaks can be a positive thing and create a lot of hype and excitement for some people, so even though I totally get that devs don't like leaks, there will always be people who get extra excited to actually see the project, and to me that's a positive thing :).
edit: Adding to this; leaking a title or a short description or something is a totally different beast for me than actually leaking a trailer or gameplay months in advance. I personally wouldn't want that, ever. Show me the product/art/game/whatever it is when it's ready to be shown. But knowing something exists beforehand rarely does me personally any harm, and usually only helps to get me excited to finally see it.