I dont get this mc. He is op at lightning magic, but just watches and doesnt care his older brother died (sure, he is reincarnated, so not too farfetched. Except after having intentionally let him die, he goes berzerk mode and reveals the secret anyway). Even though he could at any point just zap the enemy's zaps, because he is the stronger zap sage. Or their mages. Or just have warded stuff. Or anything really, he is OP.
He (and his brother) tries to save a baby, which if it survives and the coup thusly fails, is a death-sentence for both mc and his brother due to capital punishment for treason goes after the nobles entire family. Sure they might get an amnesty as the ones who saved the kid, but it is still one hell of a gamble.