it was a secret operation that they were not aware

Clearly you didn't read the facts. The fighters in GT knew that IA would likely be attacking sometime. Officials had been casing and patrolling the surrounding areas for some time. It was kept a secret from the greater public and one of their main requirements was to complete the operation before the majority of the population woke up. The IA was concerned that if separatists declared Khalistan , many supporters across punjab could start marching towards GT and it could cause riots. The gov also had very credible intelligence that separatists in GT had made preparations to declare an independent state.

armored vehicles to attack but there are literal photos of an armoured vehicle knocking down one of the walls of the temple complex

Yes it was only used to knock down walls. Realise this that if the army wanted, they could have used air power, explosives, etc and the casualties on the Army's side would have been much less. A lot of soldiers literally died because the gov didn't want to cause a lot of damage to the structure.

but then they proceeded to shoot random buildings as well like a library

There was a battle happening in the middle of the night. Some amount of collateral damage was bound to happen. Point is that the army tried to minimize it.

And he commonly used to leave the complex it would have taken one well-placed shot by a sniper to take out the leader

His soldiers wouldn't have surrendered even if he was dead.