I think I misread your post. It sounded like you were saying that the video posted above looked like 6-7 years worth of work.
I'm really not defending the guy at all. There could be shadiness, he probably spent a bulk of the money on himself/food/lodging.
After the Kickstarter % he was getting like 20K/yr I guess
Basically I think he took some extended breaks which is why it is 6-7 years of development, not unheard of for someone to need breaks to combat burnout. I assume he has a real job. I personally work on my stuff about 10-15hrs/week. This guy sounds like he cranks away and burns himself out then takes a break or goes through some personal drama.
In terms of the game, he does have quite a few "large" systems that could take a decent amount of time.
It might not look like much, but what I saw was:
Inventory+Items: Big system for any game+infinite time can be spent depending on # of items created
Abilities: Huge system + infinite time can be spent depending on # of abilities
Mob/AI system: Huge system+ # of mobs
Crafting system: More time consuming than the Inventory system
Any progression/stats/multiple playable characters
Multiple worlds/levels
World Assets & UI Assets look purchased from a marketplace, maybe didn't spend much time there tbh.
I just went through his Kickstarter and it mostly aligns with my thinking, though I got a little more background now... looks like he outsourced the Art. If he's a bad businessman, he could have easily been ripped off here, artists can be expensive. I also wouldn't be surprised if he had a lot of excuses/downtime "waiting" for art assets.
Risks and challenges
You could write a pretty big book about the risks and challenges that come with making a video game. Let's go over a few, shall we?
Challenge #1: Programming
I dedicated years of my life to teaching myself programming so I could tackle this challenge. Programming is the most important part of a video game. You can have a video game without art, but you can't have one without programming! It's difficult, it's tedious, and it's expensive as hell to find a good programmer. Luckily I apparently have a knack at it and can pretty much handle everything that comes my way. And if for some reason I don't know how to do some of the legwork myself, it's alright because I know how to manage other programmers and then integrate what they make into Soul Saga's source code! I have enough confidence to say I could program the remainder of Soul Saga within 3 months if I have all the finished art assets. Which brings us to...
Challenge #2: Art
What a general term when it comes to videos games... Art can really mean anything like concept art, 3D characters, animations, environments, particle effects, sound effects, or music. So when I tell you games need Art, let's just say that it's easier said than done. Not only do things such as concept or character models have to be the same style, every single piece of art that I have just listed needs to be the same style as everything else. This means you gotta be picky. When you're as stylized as Soul Saga, maintaining a consistent style is one of the most important things. This means that my options for artists are narrow, and that gets a little pricey. However, I have so far been successfully able to gather a portfolio of like-minded artisans that produce high quality work within a reasonable budget.
TL;DR: It looks like he bit off a LOT more than he can chew, and it's unlikely that he consistently worked on this for 6-7 years straight.