Pretty ridiculous to blame this fully on Leclerc. He made mistakes, but he's hardly the only reason they struggled. This was just a poor showing from Ferrari in general, and there's lots to take away for Singapore, both for mechanics/team and drivers.
Saying he could've "easily won" or "easily defended" is just false. "Easy" in 2024 F1 season, lol. You can be disappointed in Leclerc, but acting like he could've just covered the inside and cruised to victory is not realistic. The win was lost by Leclerc's mistake but the struggles after were not on him IMO.