It's what we call a minced oath. "Got dang" is an inoffensive substitute for "goddamn."

I guess a couple years down the road we'll need even more inoffensive words for these ones we've created. It is similar to people on social media using word seggs instead of sex because god forbid the algoritm gets a stroke

What’s offensive about goddamn? "Damn" is not even vulgar, is it?

In the context of American Christian hegemony, even if "damn" or "damned" isn't considered particularly strong by many, a lot of people object strongly to "goddamn." It's a superstition that has to do with one of the Ten Commandments: Thou shalt not take the name of the Lord thy God in vain.

“Damn” is not a vulgarity unlike certain other words, but too many utterances of “damn” will make a movie’s rating PG instead of G, “damn” will get you in trouble for cursing at a private Christian school, and I wouldn’t use the word “damn” in church unless I’m referring very specifically to God’s damnation. It goes against polite Christian mores to say “damn” or “goddamn.”