The music that the youth was making was already drill-like in the same time period that Chicago drill was emerging and in the years leading up to it.
There was a wave of homegrown gangs like YGz, YBz, OY, OGz in the Bronx and Harlem and Hood Starz (Cho) and Wave Gang (Woo) in Brooklyn. This led to new gang wars, the influence of early YouTube and especially those Philly rappers, and NY-based hood/hip hop DVD’s like Smack, led to the WeMobbin series where a lot of this early proto NY drill was featured usually in freestyle form or in early poorly mixed and mastered tracks.
In that time Jadakiss “Child Abuse” beat went platinum every gang seemingly had their own version
When Chief Keef popped there was a huge gravitas because they was on the same shyt, with a similar look, he was the first authentic young nikka signed in a minute at the time labels weren’t investing in them. It was a blueprint that could be followed and that was relatable for NY youth at that time. It was the blog era and they were signing every man, 20 something year olds. Social media and virality and access to home production software and videos and shock value plus kids in real gang wars it opened up a way to get exposure and signed and diss the opps.
Also, that club shyt is pretty huge over the last few years in the East Coast music scene down to mainstream.