Not true. It does have bearing.

It's not the only factor on whether or not you will be successful though. And yes, even intelligent people supported Hitler and Trump.

Being smart doesn't mean you have good character. But, there are different kinds of smart and people of good character usually have one kind of smart. Further, certain paths of achievement can only be attained by determination and a willingness and desire to see things though. Patience, hard work, integrity, asking for help when you need it, drive, openness, etc.

Or are you suggesting that none of those qualities or character traits are useful or necessary in building a solid relationship?