Some behaviors did have to be encouraged, but from what I understand, the behaviors were encouraged through small indirect nudges instead of specifically adding

Some behaviors did have to be encouraged, but from what I understand, the behaviors were encouraged through small indirect nudges instead of specifically adding code to the bots to tell them a certain behavior is good. For example, the devs said that the bots never tried to fight Roshan on their own because he does a lot of damage, has a lot of health, and the bots don't know what the reward for killing him is. To encourage the bots to try it, Roshan was given artificially low health so the bots would kill it to see what happens. Once the bots learned that there are rewards for killing him, the devs started to randomize his health between very high and very low values so the bots could get a feel for when they are strong enough to try and kill him during a normal match.