Do you have any actual evidence for that? Intel does care about power efficiency - they've been making mobile CPUs for decades. And I don't think they are lacking intelligent chip designers.
I would need some strong evidence to make me think it isn't the ISA that makes the difference.
Basically, x86 uses op caches and micro ops which reduces instruction decoder use, the decoder itself doesn't use significant power, and ARM also uses op caches and micro ops to improve performance. So there is little effective difference. Micro ops and branch prediction is where the big wins are and both ISAs use them extensively.
If the hardware is equal and the designers are equally skilled, yet one ISA consistently pulls ahead, that leads to the likely conclusion that the way the chips get designed must be different for teams using the winning ISA.
For what it's worth, the same is happening in GPU land. Infamously, the M1 Ultra GPU at 120W equals the performance of the RTX 3090 at 320W (!).
> Isn't Lunar Lake first mobile chip with focus on energy eff?
Not by a long shot.
Over a decade ago, one of my college professors was an ex-intel engineer who worked on Intel's mobile chips. He was even involved in an Intel ARM chip that ultimately never launched (At least I think it never launched. It's been over a decade :D).
The old conroe processors were based on Intel's mobile chips (Yonah). Netburst didn't focus on power efficiency explicitly so and that drove Intel into a corner.
Power efficiency is core to CPU design and always has been. It's easy create a chip that consumes 300W idle. The question is really how far that efficiency is driven. And that may be your point. Lunar Lake certainly looks like Intel deciding to really put a lot of resource on improving power efficiency. But it's not the first time they did that. The Intel Atom is another decades long series which was specifically created with power in mind (the N150 is the current iteration of it).
> It is like saying that Java syntax is faster than C# syntax.
Java and C# are very similar so that analogy might make sense if you were comparing e.g. RISC-V and MIPS. But ARM and x86 are very different, so it's more like saying that Go is faster than Javascript. Which... surprise surprise it is (usually)! That's despite the investment into Javascript implementation dwarfing the investment into Go.
Actually, if you had made an opposite example, it might have gone against your point. ;) C# gives you a lot more control over memory and other low-level aspects, after all.
I would need some strong evidence to make me think it isn't the ISA that makes the difference.