i'm not sure it's correct to say that lisp's 01959 approach to defining variables is a 'confusing break from conventions' established by c, which originated in 01972 but didn't support 'sticking variable definitions anywhere' until 01999 with the 01999 revision of the iso c standard. i would rather say that sticking variable declarations anywhere, a feature i believe was introduced to the mainstream by c++ around 01990, was the break from conventions. almost all the languages i'm familiar with from before that required you to batch up local variable declarations at the tops of scopes: c, smalltalk, pascal, scheme

the exception is basic, where you could defint i or dim x(128) at any point, but it would be an understatement to say that basic's conventions were not widely emulated by other languages