Sorry, where did Martin Richards supposedly make this decision?

That's how variables are declared in BCPL, the language he designed and implemented in 1967. Keyword "LET", comma-separated list of names, "=", comma-separated list of expressions (that will be used to initialize the variables). For rare cases when one deliberately wants to leave a variable uninitialized, constant-valued expression "?" exists.

Anyway, why is this syntax atrocious?