It's usually just basic NLP or basic challenging/proving there is little evidence to the fear and it isn't complicated.
And lots of 'phobias' are flimsy in their basis and easily solved. Not all or probably even a majority but many are and many people haven't seen a MH professional or even a poorly 'qualified' counsellor.
Many people with 'phobias' just aren't used to anyone challenging it; because they haven't sought out decent help. That's not to say many, many people have and it hasn't helped.
I 'cured' agorophobia in one meeting with someone who hadn't left the house in 4 years - not even to go to the birth of his youngest child. What did I do? I said - please put your shoes on, we're going for a walk and when he said I can't, I said put your shoes on please, we're going for a walk, it'll be fine I promise.
So we did and it was fine and the next week he was independently picking his kids up from school. He came from a culture where the man had the ultimate say in everything and was never questioned or challenged. I challenged it, proved it was fine and so it was. I was viewed as some sort of God by his family when it was as simple as challenging the idea when no-one else had.
Another time I engaged in several sessions of CBT with someone who wouldn't leave the house because they thought they'd be murdered. After lots of well thought out sessions about his base fears and why he specifically feared murder (related to early trauma) I was a bit frustrated by the lack of progress by the end and said 'you're far more likely to be run over on the way to the shops you know'. That's true he said..started going off to the shops with no problems.
Sometimes all it takes is for someone with a 'professional reputation' and/or someone that the person trusts to 'unlock' an irrational fear or a pattern of behaviour that the person and their nearest and dearest have helped to entrench.