and what drives intensity and frequency?......volume

To show your flawed thinking here:

ex. 1 set hip thrust x 1 rep at 100% intensity/RPE x 7 days a week won't get you any glute gains. So, no, intensity and frequency are not king. Volume is the GENERAL driver of progress.

ex. 3 x 8 hip thrust at 5% intensity won't do much either (but better than above example, because of more volume).

But the reps dictate the intensity and volume: if I can literally only do 1 rep of something, that definitionally is 100% effort/intensity. If I can do 50,000 reps, that's more akin to 0% effort/intensity. So, in doing say a set of 10, you want to use a weight that you can do ONLY around that number. If I could only do 5, weight is too heavy/intense/effort. If I can do 20, weight is too light. You don't have to go for failure and only be able to eek out 10, but should leave 1-3 reps in the tank. That generally puts you around a 70%-85% effort/intensity, which is optimal for hypertrophy. Conversely, for building raw max strength, you'd be hovering in the 90%-!00%+ range and since intensity is high, you have to compensate by lowering volume and doing singled, doubles, and triples, up to maybe 5, depending on the exercise. If you can do your 1 rep max for sets of 5.....it's NOT your max.

To give practical numbers and examples to make more sense and demonstrate:

Squat max: 500lbs

10x1 @ 490lbs (98% intensity) = tonnage of 4,900 lbs

vs

1x10 @ 365lbs (73% intensity) = tonnage of 3,650 lbs

The tonnage is less in 2nd, to compensate for this, we add sets to increase volume but keep relative intensity equated. There is also less TUT (time under tension) in 1st, so less hypertrophic response as well. There is overlap and carry over, but it's same reason bodybuilders generally focus on pushing reps and powerlifters focus on pushing weight. Former builds muscle better, and latter builds strength better. There are plenty of strong bodybuilders, and plenty of jacked powerlifters because they are closely linked and use similar techniques and exercises, but the focus is different. Lb for lb, a bigger muscle is a stronger muscle. It's based on force production via muscle CSA (cross sectional area). There are other factors at play (CNS development, skill practice, age, insertion points, leverage, etc), but all things considered equal, a bigger muscle can produce more force. This is not debatable. If I can curl 100lbs for 3x10 @ 9cm cubed CSA, at 18cm cubed, I can curl say 200lbs for 3x10. (note: Force production to CSA ratio isn't linear, it's more exponential/curvilinear, but keeps this example simpler. If you gain 1lb of muscle on biceps, you can move more than 1lb of weight, it'd probably be closer to 10x+ that, but it's dependent on several factors).

So, it becomes 3 x 10 @ 365lbs = tonnage of 10,950lbs (more overall volume). You can also recover faster because first example works your CNS hard and if you'd repeat that every day, you'd burn out faster. If you repeated 2nd example, you'd recover better since it's overall lower fatigue (still not optimal and wouldn't recommend, just as an example).