BU was actually just a fork of core 0.12 (all core 0.12 bugs included)
bu just tweaked a few lines of code to allow dynamics and left it out there for the community of independent devs

it wasnt until fixes were done that people spotted some nodes hadnt upgraded post-fix. so exploited such.

funny part is assert(0) was actually a exploit that was able to harm core 0.12 too

also funny part is that BU devs didnt create it, and people didnt exploit it ntil it was patched.. which then made exploiters realsie that some users were not yet patched against it..

P.S
having BU screw up is actually a good promotion of why diverse brands SHOULD exist on bitcoins main net.

imagine however if EVERYONE was just running core and only core.
then imagine there was a issue with the db locks of the blockchain data..

oh wait.. no need to imagine it.. 2013's leveldb update which  didnt factor in something when moving forward .. causing several hour stall and orphan event.
...

but now imagine if bitcoin remained diverse with many different implementations . if one codebase goes down.. only a few nodes go offline and everything else continues as normal.

so all you crybabies that want core centralisation .. imagine future events like the 2013 leveldb event
anyone who wants diversity. imagine this months 'oh well a few nodes went offline' no big deal

diversity is good. not bad.
keep bitcoin diverse and decentralised and independent. dont advocate for centralised power house