Is my husband faking being dumb?

My husband is a very sweet person. He can just be dumb at times. A lot of the time actually. His mom has always made jokes about my husband being blonde and dumb. He is blonde like his dad and the only blonde out of 4 siblings. He has 3 sisters and 1 brother. They all have brown hair. His mom is also a brunette and as long as he could remember his mom would make jokes every time he made a mistake saying "Oh he's just blonde." "That's the blonde one." "He's definitely a Blondie." My husband does some of the idiotic shit.. And laughs about it. He washed his pants with his phone in it. He tries to fix everything with duct tape. The hand on the oven broke and he used duct tape to fix it. I asked him to thaw out some chicken and instead of putting it in cold water to thaw quickly he just put it in the fridge. I was kind of talking to his brother about it because everyone knows he does stupid things and how brother said he wasn't always like that. He was really smart and was a straight A student on middle school. I asked what happened then and he said he doesn't know. He thinks with his mom constantly making dumb blonde jokes every single time he made a mistake he just started living up as the dumb blonde. He became the class clown that does dumb things and barely passed high school with D's and C's yet got a 1520 on his SATs which I did not know he scored that high on his SATs. So does my husband just fake it?

Edit: I know having book smarts and common sense are not the same thing. His brother however said he didn't always just do really stupid things. I didn't even know he had book smarts until his brother told me his SAT scores because he barely passed high school. His brother said he started acting more time as time went on leaning into the dumb blonde thing because since he was small his mom constantly made jokes about him being a dumb blonde. I married him because even without the most common sense he's a very kind sweet person who will go out of his way to help anyone.

Edit 2: Nowhere here did I say I think he's dumb because he's blonde. I said his mom made jokes about it. I even said his brother said after years of his mom calling his stupid for no real reason besides him being blonde he started leaning into the dumb blonde thing. I don't think hair had any correlation with smarts. I'm just asking if he's pretending he's dumb because since he was little his mom called him dumb.