Why do I get anal fissures?

F25, two years ago was my first experience with anal fissures and was pretty bad. It hurt, it bleed, but the worst of all was the medication ( a cream) that made my butt’s skin really rashy and sensitive. I freaking hate the scratching feeling, it’s pure torture.

Back then i was done a colonoscopy that showed no sign of any damage or deeper problems. And then it just healed. Now, I’m fighting again. This time the pain is much better, no blood and easy toilet going but the sensitive skin and rash is torturing me again. I made really big changes to my lifestyle since the first time - working out 4 times a week ( climbing and weightlifting ), good hydration and healthy eating. Then why do I get the fissure again? Can someone please advise me? I can bear through the pain, I can go through some small surgery to burn the fissure so it can heal but I need to know how to prevent it for future.

I will be also really thankful for advices on how to heal the rash. I am using coconut oil and baby cream and it seems so help ( this is what my doctor prescribed me the last time) I also learned my lesson and I try not to touch the area at all.

More info: i dont ride bike, i dont do anal sex, i have an office job but i am really active person who needs to take walks and do sport so I am overall in a really good physical condition.