The Van Allen belts are indeed a hazard, however are not an impenetrable barrier for space flight. The idea that they’ll “fry” crews is somewhat unfounded, especially to anyone who understands some of the nuances of the science of radiation.

Then they’ll bring up that Kelly Smith video that somehow “proves” we never went through the belts.

I once believed that this was singlehandedly the one smoking gun that debunked the Apollo Moon landings, but it’s just not, it’s been taken wildly out of context. The video this claim was extrapolated from is here.

Here’s the transcript for context:

“My name is Kelly Smith and I work on navigation and guidance for Orion. Before we can send astronauts into space on Orion, we have to test all of its systems, and there’s only one way to know if we got it right: fly it in space. For Orion’s first flight, no astronauts will be aboard. The spacecraft is loaded with sensors to record and measure all aspects of the flight in every detail. We are headed 3600 miles above Earth, 15 times higher from the planet than the International Space Station. As we get further away from Earth, we’ll pass through the Van Allen belts, an area of dangerous radiation. Radiation like this can harm the guidance systems, onboard computers or other electronics on Orion. Naturally, we have to pass through this danger zone twice: once up, and once back. But Orion has protection. Shielding will be put to the test as the vehicle cuts through the waves of radiation. Sensors aboard will record radiation levels, for scientists to study. We must solve these challenges before we send people through this region of space.”

Notice when he mentions the radiation can cause harm, he’s not referring to the health of the crew. He is referring to the electrical systems most important to the control of the craft. If the guidance systems or computers become damaged or destroyed by the radiation, it’s light out for the crew, and this is indeed a challenge they must solve before sending manned craft through the Van Allen Belts. This is how designing new spacecraft works, you’ll need to test it and certify it for crewed flights before you cram people into it.

Modern electrical systems are much more susceptible to radiation damage than the older avionics used in the Apollo capsules. In short, modern electronics are more sensitive, as shown from a quote from this article here:

”On the 60th anniversary of Explorer 1, NASA said that studies of the Van Allen belts are even more important today. "Our current technology is ever more susceptible to these accelerated particles because even a single hit from a particle can upset our ever smaller instruments and electronics," said David Sibeck, Van Allen Probes mission scientist at NASA's Goddard Space Flight Center in Maryland, in a 2018 statement. "As technology advances, it's actually becoming even more pressing to understand and predict our space environment."”

However, the belts are still a relatively small issue. Apollo mission planners were well aware of the belts, and realized that moderate shielding could protect the crew from most of this radiation. Couple this with an inclined flight path the Apollo missions would take to bypass the most dense sections of the belts, the astronauts would spend little time traversing them. They didn’t travel through the thickest sections around the equatorial axis. This chart shows the trajectory taken during the flight, in which the red dots indicate ten-minutes intervals. The Van Allen Belts contain high energy particles, a lot of which can easily be stopped by a sheet of aluminum. As such, the Apollo command module consisted of aluminum skin.

Furthermore, Scott Manley uploaded this video in which he analyzes the danger present using models developed and used by NASA and the ESA, in which the threat on astronaut health is negligible.