Classic crotch blowout from the photo.
Main culprit is almost always thigh frictionβinner thighs rub together with every step, wearing out that exact seam spot over time. Tight fit in the crotch, lots of sitting/bending, or weaker denim seams make it worse and happen faster on repeat pairs.
Try roomier thighs or reinforced/gusseted crotch jeans next round. Happens to tons of guys!