To break it down:
Rock vs. Pop
Rock made the most profit when culturally it became a part of Pop culture. This started to die off in the 80's but hair metal became a sensation. Hair metal was then killed off for the next wave of acts that were assimilated into the record industries more reliable formulaic machine for hits. Record labels like Mercury began purposefully killing off hair metal bands.
Eventually pop punk, grunge, nu metal and other genres were manipulated in the main stream to become represented by the producer controlled music making machine.
Why have a band completely in control of their music and writing what they want when they want? Would you not make a lot more money having an inner circle of producers who have mastered making hits, and creating the mainstream landscape of what a hit is?
Instead of investing in bands who may go any which direction, it is more lucrative to hire performers who will treat it as more of a job, and sing the songs written for them, dance to the choreography created for them, endorse the products your sponsors give to them, etc..
And if some kind of rock is popular, we'll study the trend with a focus group, then get the producer to hold their hand through a simple track, we'll get a director to come up with a topical video to get attention, the lyricist's will come up with a catchy provocative line that will be repeated until it gets into people's heads, then the people will repeat the lines and memes to advertise for us, for free. Wardrobe will get them something trendy, then we'll get PR to get some interviews, and create some kind of juicy scandal for the group.
Then we'll pay stations a lot of money to play us often, iTunes to feature us heavily, Youtube to recommend our video, etc...
Then we'll make a bunch of money, give a good chunk to execs, producers, lyricists, then pay off all the marketing, and other costs, and we'll throw a few bucks at the band. Oh wait, we 'advanced' the band all sorts of money when we paid for that new guitar, the gas in the tourbus, their catering, etc etc... Better cut down how much we gave them.
Then compare that to moderately successful VK bands filming a PV in the parking garage a thousand other bands played in, in some flame retardant outfit that 99 percent of people would not be caught dead wearing, and a bass player who looks better than most girls, playing a song in a low drop C tuning, over vocals still high pitched as hell, in a style of music that is no longer popular or never has been popular in the mainstream.
Then they take that PV, and include it as a bonus for the limited edition, cd only release not on iTunes, and not uploaded to Youtube unless somebody decides to do it against their wishes. And the majority of viewers are international viewers since Japanese have their own sites and ways of digesting media to choose from as well.
And they compete in the second biggest music market in the world, with a huge amount of other independent visual kei artists, many of them producing their own music, and not having doors opened to them, no big funding, and a lot of bands still survive somehow, and bands like Royz, Kiryu, etc.... enter the top ten of the charts repeatedly beating tons of major produced and marketed acts, despite being the antithesis of worldwide pop culture and trends.
Then you have bands like SID, and lots of older bands like X Japan, Luna Sea, Dir en grey, who have made more money than most pop artists, have been around longer than KPop was a 'thing', and will be referenced as long as there is VK.
But in terms of Youtube and worldwide presence, Korean Pop has a very large presence, has several connections to worldwide pop culture where it isn't such a huge step, they are just rapping and twerking in a different language. The Korean government has also heavily funded Korean media on the global stage, from the Korean Wave of film that had a regrettably short life, to KPop now. Japanese individuals and companies have actually complained about not representing Japanese workson the worldwide stage, I even remember Gackt talking about how they are failing to promote Japanese work outside of Japan. But at the same time, Japan has a much more insulated subcultural make-up, and is not AS rapidly molded and influenced by Global and especially American trends. So I definitely think certain cultural exports from Japan are hard to find an audience for, while some others, like anime, games, manga, JDM, etc... have been some of the most influential things in pop culture and subculture history.
Not sure if I answered the question or even tried to, but ah well.