If C is so evil why is it so successful?

While one might argue the proliferation of BASIC on micros followed from BG/PA & SW/SJ, I'd say their implementations were following a trend rather than initiating it. BASIC was gaining prominence prior to their implementations of it. It was in all 3 of the pre-microproc personal computers: HP9830, Wang2200, IBM5100. It was becoming popular and spreading in the small-business world through the Pick-based systems (albeit an extended version of the language). It had gained awareness through the educational system and timesharing systems. All prior to MS & Apple. As bad as it was, it was present in the right place (small, easy to implement, interpretable & easy to use) at the right time (the nascent small-system and personal computer era).