Why does my hair get frizzy and wavy again after blowouts?

My mom used to do my hair with a blow dryer and a blowout brush for years. I wouldn’t say my hair is completely healthy. I wash my hair once a week and do coconut oil hair masks before. I tried using my revlon dupe but my hair goes back to normal and gets frizzy after. It doesn’t stay that way for some reason.. but when my mom does it it does. What should I do?
Why does my hair get frizzy and wavy again after blowouts?
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