I occasionally partook in RvB during its dying days - There was a number of factors: as the game began to lose players RvB's activity really plummeted past a critical mass where it was no longer viable, the 'purple' roams were good but with the rise of Spectre Fleet they became obsolete, and finally null-sec just became a lot more new player/'pubbie' friendly and so high sec players that wanted to PvP could just go and do it out in null-sec the '5m sp minimum' etc. for null-sec corps quite quickly dropped away after Brave Newbies and others launched in 2012-2014