I saw a guy dressed in a nice business suit and a Mohawk haircut

No, I don't think his haircut should be a factor.

Hair, tattoos and wardrobe usually are a factor depending on the job

I wouldn't want a lawyer with a mohawk for instance

It least he wore a suit, I guess.

He won't get the job. I personally don't have a problem with it but a lot of people would

Depends what the job is. If he's going for a job at a law-firm, likely he won't get it. If he's going for a job at a tattoo parlour, they might be impressed he took it so seriously.

How do you know he was going for a job interview?

No, but it might depend on the job. Are elderly retirees going to trust him with managing their hard-earned accounts? Would nervous family trust him with performing life-saving surgery on their loved one? Maybe. Maybe not.

If the job was concert promotions or tattoo artist, then the hair might be an asset.