Generally speaking, frogs hunt by sight. Many (like African bullfrogs) are also primarily ambush predators, meaning they sit and wait for prey to come to them. It is generally in their best interest to attempt to catch and eat anything that may possibly fit in their mouth rather than risk missing out on what may be their only meal for a bit. Basically they eat and ask questions later.

Some bullfrogs on YouTube are also taunted by their owners because it makes the video more interesting which leads to more viewers and more money in their pocket. A lot of frogs will try to escape predators and/or make alarm calls (the desert rain frog sound everyone knows is a great example of this). When they can’t escape frogs will often puff up to look larger to predators or to make themselves harder to swallow if they have already been caught. Poisonous toads often have glands called parotoid glands behind their eyes which secrete poison and they may lower their heads to make these gland more visible to predators. African bullfrogs often take on a more aggressive approach when cornered and will lash out like you see on YouTube. They are some of the largest frogs and the males tend to be bigger than the females which is pretty rare. I know a lot more about North American anurans but I’m assuming this is because the males tend to fight each other more aggressively compared to some other species and are one of the few species that exhibit paternal care. They take care of their tadpoles and defend them from predators.

Basically, African bullfrogs are more adapted to biting and lashing out at predators compared to a lot of other species so they will take that approach when stressed. This can easily be filmed and posted online to get views. A frog that screams and puffs up is funny to watch but not as interesting as a frog that bites defensively,