It's been awhile since I had seen this swing sequence, but here's a sequence of Hogan in the 1930's, before he discovered the 'secret' to stop his hook.
What do we know about snap hooks:
1. The clubface is very closed at impact if it is a 'true' snap hook' that starts low and left and then hooks over.
2. The path has to be inside-to-out in relation to the face. Which is very easy to accomplish if the face is very closed at impact. Why? Because if the face is 5* closed at impact and the path is square to the target at impact, then you actually have a path that is very inside-to-out in relation to where the clubface is pointing.
3. Hitting down on the ball rotates the plane line to the right right, which makes a hook spin much more likely.
So, what changes do I see that Hogan made from his 1930's swing.
For starters, I will get out of the way two big changes that were reported that he made that got rid of his hook.
1. He weakened his grip.
2. He cupped his left wrist at the top of the swing by basically feeling like he was rolling open the club on the backswing as far as he could with his left arm.
You can't really see those two changes from this sequence. The grip looks pretty good here, making me think that the grip may have been weakened pre-Secret. Remember, Hogan had a 'reminder' on his grip...which was about the size of a piece of wire hanger at about the 5 o'clock part that basically forced the golfer to grip the club weak. I believe pre-Secret his clubs were created to make it almost impossible to hook. But he kept hooking them until he discovered his 'Secret' and then stuck with how his clubs were designed (flat lie angles, super duper stiff shafts, etc) because he'd gotten so used to them. And that's why I also believe he had that reminder on his grip pre-Secret.
Usually when people get into Hogan's 'secret' they actually talk about how he shortened his swing. Hogan did indeed have a very long golf swing.
Not very far off from John Daly's old backswing.
In fact, I've read that there are scientists who estimate that Hogan's driver clubhead speed was around 122 mph pre-accident. I also heard that Hogan did compete in some long driving contests in the 1930's as well. His swing has always looked powerful and here it looks like if he hit one well, it was probably amazing to watch, particularly for a man of his size.
However, here's a video of Hogan's swing, taken after he discovered the secret, but before the accident.
Not exactly a shorter swing in my book. But there's still a large contingent that think Hogan didn't get good until he shortened his swing, which is blatantly false. Even worse, they tend to use that information and think "short swings = more accurate and consistent ballstriking" which I do not believe to be true.
The big differences I see are actually at impact and post impact.
One of the things that instructor Geoff Jones (aka SliceFixer) stresses is that Hogan had the hands moving 'low and left' past impact. This is basically the CP Release in MORAD terms and Hogan did it with an angled hinge. Geoff also talks about how he doesn't like to see the hands 'crossover' past impact because that essentially means that the hands are not moving 'low and left.'
Also, take a look at Hogan from the target view.
I think it's very very difficult to make a 'crossover' move without swinging out to the right. I also think part of that crossover move is dependent on how well you pivot post-impact. Look at the target views, Hogan has much more pivot post impact once he has discovered 'the secret' than in his 1930's golf swing. I think some of that had to with Hogan cupping the left wrist, but I also think a lot of that had to do with years and years of practicing and playing with equipment that had unbelievably stiff club shafts, flat lie angles, weighed heavy and the reminder in the grip.
Also, look at Hogan's right arm. It straightens out much more quicky in the 1930's swing whereas in the post-Secret swing it is 'saved' a lot more. That IMO, is a big function of post impact pivot.
It's also pretty easy to see that Hogan hit well down on the ball in the 1930's video.
So, he basically had a swing that was just plain suceptible to hooking the ball. Steep Attack Angle (the post-Secret swing actually seemed to have a much shallower attack angle) and he swung out to the right more and really closed the face post impact. If he wasn't totally 'on' with his face angle, chances are it got closed quite a bit at impact and with his steeper attack angle and swinging more out to the right, there's a recipe for a snap hook.
Then to look at his post-secret swing. He appears to have a more shallow Attack Angle (but probably still hit down on the ball to a degree), swung to the left, and kept the clubface square past impact which made it tough to hook the ball.
Lastly, let's just take a look at a swing sequence of Tiger Woods.
If you look at it post impact, there's a big crossover there.
Let's look DTL:
It looks to me that Tiger is swinging out to the right a bit with what appears to be his 3-wood.
That's not bad provided the golfer is hitting up.
However, we know from Trackman data that Tiger has an attack angle of -3* with the *driver*. With the 3-wood it's probably as steep if not steeper.
And what is Tiger's problem shot? The dead right block.
And if you are hitting relatively straight, but dead right blocks, the path *must* be out to the right a bit otherwise you would see a big push with a huge slice attached to it. Basically, the dead right blocks are:
Open Clubface + inside-to-out path (in relation to the target).
But that's just an example why I believe the 'crossover' of the hands basically means the golfer is swing out to the right. Not that it's bad, but indicative of what the golfer does and the world's best golfer, who has a crossover move, has trouble with a shot that requires the golfer to be swinging out to the right a bit.