Why "effectuate"? From what I've googled, it seems to be a direct synonym of "effect", so what's its raisin debt?

"Effect" as a verb is basically a muddled mess. The main reason that people have problems spelling the affect/effect pair is that they just don't fit together well. If you affect something you have an effect on it. Using effect as a verb or affect as a noun just sounds wrong. Effectuate has the advantage of being unequivocally a verb and there's no chance of confusing it with affect.