Why has my hair gone from straight to curly?

Ive never cut my hair super short but i did cut it to chin length last year, and since its started growing back (its a bit down my back now) its gotten really curly. i mean not super defined curls, but there are large ringlets if i dont comb it, if i comb it it goes to really wavy. ive never had curly hair before, maybe wavy at the most as a child(but i always had it in braids, so who knows), Im 20 years old so im over puberty, and i havent changed my routine for years. i dye my hair every so often, but it doesnt feel unhealthy. no one in my immediate family has curly hair. my hair is pretty thick and has some texture normally, but i really dont know how to handle my new hair very well, its frizzy and gets tangled soooo much now lol. its really taken a bit to get used to ive never heard of this happening before, although ive seen it in reverse. so does anyone know why this would happen?