Regardless of wether it’s a weak spot or not, I don’t think the guy was aiming for anything in particular, he just placed the explosive wherever he could, though at the end, as he pulls the safety pin, you do see him aim the warhead of the IED towards the tank. It’s basically an improvised explosive device fashioned from a Tandem RPG charge, which would be more than enough to go through the armor of the tank at that place and angle, since it’s basically aimed at the turret ring of the tank, however depending on just the exact angle it was when it went off and where the tanks turret was pointing it could have different outcomes from damaging the turret to other external sensors and the main gun, it could most definitely kill the crew too.
The side armor of no tank is strong enough to withstand a tandem RPG charge on its own, but given the ERA and other add-on armor, it would be possible to withstand the hit, though it would still likely damage the tracks and score a mobility kill. A static tank is as good as dead.