Is the issue that the blowout causes the wheel to suddenly turn to one side, and the driver is unable to keep the wheel pointed the right way?
Or does it cause some other issue like drag? I can see how the smaller wheel diameter would cause braking to be increased on the side that blew out.
I don’t understand why this happen in a large truck or motor home but not a car. I’m not accepting answers along the lines of “But it’s bigger and harder to control you idiot”.
Only if the driver doesn’t have a firm grip on the steering wheel with BOTH hands like they’re supposed to.
When you have a front blowout, you don;t brake. You keep the power on lightly until you regain steering control, letting the friction of the blown tire slow you and then GENTLY applying the brake and pulling onto the shoulder. No motorhome or loaded large truck can handle as well as a car because of design compromises that have to be made due to their size and weight, you idiot. 
Non-independent solid axle under trucks and motorhomes is much harder to control with a blown tire than an independent suspension that you will find under virtually every car.
Darn , there goes my answer .
Also Motor homes are driven by a large percentage of elderly people with questionable driving skills.
Partly due to higher center of gravity, relative to vehicle track width.
Imagine a pyramid.
The top is at the vehicle CG height; the bottom corners are where the tires touch the ground.
A tall narrow pyramid is easier to tip over.
A flat tire has more drag than an inflated tire. It creates a similar scenario to a brake suddenly being applied to only that one front wheel.
The solution is to floor it until the RV is under control. The reason behind this is force vectors. In normal driving, you’re going straight, and your force vector is pointed straight down the road. Once the tire blows, there’s a force pushing the RV to whichever side the blown tire is on, which moves your force vector to a point between straight down the road, and to the side of the bad tire. Accelerating increases the force pushing the rig down the road, which moves that force vector closer to straight down the road and makes it easier to control. Once it’s back under control you can gently let off of the throttle and stop the RV.
This old video has good visuals to explain this:
The video agrees with you, but I’m going to pass on flooring it. I think I’ll just steer against the pull, let off the accelerator, and let it coast. I can’t imagine hearing “Bang! Fwop, fwop, fwop” and slamming down on the gas. I just don’t think I could force myself to do it!
Our motor home had dual stabilizer springs on each knuckle. For a reason.
Great answers so far,
. Solid front axle.
. Bigger vehicle and might not be properly loaded (aka weight balanced).
. Elderly person with questionable driving skills.
Pick one or any combination of the 3…And there are probably others not mentioned.
I wonder if it also has to do with the greater gear reduction in the steering which requires the driver to turn the steering wheel more to correct the situation.
I wonder if that video that suggest going to full throttle is correct. It seems more dangerous to increase speed. Just coast until the steering problem is corrected. It looked like the driver only had to turn the wheel 1/4 of a turn to correct the situation. This is quite doable even though a driver who isn’t expecting to need to do this may not do it.