No.
I think he was one of first successful viral music acts on YouTube but if we're looking at the entirety of this last decade and the one that preceded it.
You have to consider :
The crunk,trap,snap and jerk movements.
The artists within those sub-genres which helped to foster and curate those formats.
The proliferation of online platforms for distribution of music. Back then it was primarily music blogs and datpiff
Now there's soundcloud,Pandora, youtube, Spotify etc.
And music magazines which primarily focused on print now shifting to websites and recorded media. They're repositioning themselves as taste makers and gatekeepers.
Because of this they're able to influence WHO gets seen the most and WHAT gets listened to.
Then the proliferation of power, fast hardware and cheap accessible music software makes it possible for most anyone to begin making music.
I think once you look at those factors and acts like 3 6 mafia, Gucci mane, lil Wayne, Lil Jon and more. You put Soulja and his place as far as influencing SoundCloud rappers into perspective.
In short:
He isn't a legend and his influence while there isn't what lead us to today.
In fact I think it could be argued that Soulja boy is a creatively bankrupt bedroom rapper whose suffering from delusions of grandeur and stills presents himself as one of the greats despite his most relevant hits being nearly a decade old.
This same rapper has go on to find out his actual musical talent and ability is pretty limited and this lead to copying any of his peers which seemed to be sorta hot.
This is the only correct answer. 2006-2009 were when the whole going "viral" thing became a way to advertise.
We had a looming recession so many music publications had to let people go/ focus on their digital content. They also did this to combat music blogs, which were particularly popular around this time and started the whole "tastemaker" and incessant need to be "first" to find the newest act. Luckily enough, albums at this time were not better than most mixtapes-- and we had the novelty of rappers hopping on someone elses beat and just taking over on the same day the original artist released a track. We saw some of this we G-Unit mixtapes, but you had to wait for some of those. This was damn-near instaneous.
Myspace, was also a HUGE factor in this. People realized they didn't have to be discovered by following acts on shows and could just post their own shyt on a page. Myspace also supported video content, so people started posting their own videos as well. It also led to a direct-to-consumer feel. You could actually have a conversation with a musical act by leaving a comment on his/her page. The artist was able to directly respond to people who followed him/her on their page. This was a form of connectivity that most people have never considered before.
Speaking of connectivity, PHONES! You could purchase ringtones or just download full tracks on your phone. The internet became more accessible because of an increase of "Wireless" connectivity.
As for distribution, blogs, youtube and datpiff were the easiest ways to get music at the time. It was inevitable for people to start seeing that and services like, Soundcloud, Pandora, Spotify, Apple Music to pop out from how music was consumed.
Soulja is influential, in the sense that he was
one of the earliest to see this and become successful, but most of the indie acts at the time were already doing the same. Despite this, he's proven time and time again that he could only mimic his peers and the last time he was relevant was when people were planking.
