How Did The NRA Become So Powerful?

People across the country have spoken out against the National Rifle Association.
The outrage is largely in response to the Parkland high school shooting. Advocates for stricter gun control have called out politicians. They claim the NRA’s donations have influenced them not to enact stricter gun laws. Even President Trump accused fellow Republicans of being "afraid of the NRA." The NRA has a long history of gaining political power. It's held power over legislation for decades.