That's a very good question.
It's a mix of elements that come together at the right time and place and capture the attention of the biggest possbile demographic because SOMETHING in the IP itself is able to break the barriers between demographics to appeal to a big number of people, somehow.
In the publishers minds, this translates to "guy with a gun shoots things", so we get all these IPs that are just guy with a gun in brown and bloom shoots things, etc.
But then you have shit like the souls series, where it just wanted to be it's own thing and it got big by word of mouth, then exploding once DaS1 got released.
So you see, IPs can get big in a numer of ways, but some ways are safer than other.
Let's put it this way:
You're the CEO of a video game company.
Someone suggests to you two possible projects you can invest in.
On one side, a brand new IP with unique mechanics and new ideas that might sell, or might fall into obscurity resulting in a huge monetary loss for your company.
On the other side, you can choose to finance a new entry for an already estabilished IP with estabilished mechanics using the same formula that made you millions so far, a very stable, secure investment.
Factor in the fact that shareholders are breathing down your neck every day and want more money, then you gotta pay all the people that work in your company, and add to that your own greed.
Of course the braindead decision is to invest in the pre estabilished, already succesful IP.
And thus this is how this industry shits out the same things over and over again and when something new makes it big is mostly pure luck mixed with word of mouth.
My biggest advice to Holla Forums is, explore new, obscure games.
Buy those fucking games.
Shill those fucking games to other video game enthusiasts, and make them buy too.
That's THE ONLY WAY new, original IPs will ever make it big.
This is how Souls got big, this is how Monster Hunter got big, and so on, create, mantain and take good care of the communities for small, new IPs and make them big over time.