Sequoias like most Large SUVs end up doing mall crawling, soccer mom duty, "manly" minivan duties, ect. The large majority of owners of larger SUVs are not interested in touching dirt, but either utility and/or "Bling Factor" which is why some of them rock Dubs or taller.
The other main thing is that the Sequoia is very large which is not something you always want on the trail. I personally avoided the Sequoia because it felt too long and easy to hang up on trails vs. the 4th Gen with the V8.
Typically when people think of a Land Cruiser they mainly think of the LC100 & LC200's; the LC80's and older are pretty popular to modify and off-road. The LC100 & LC200 are not as popular to modify in the states mostly because starting with the LC100 they became "baby Lexus" vehicles. The Lexus LX470 & LX570 actually share a LOT in common; its a bit more than a re-badge with extra leather, but I'd say is like 80% similar parts. The price for many of these used LC100 & LC200's are still very high and its a pain in the ass to de-content a bunch of useless luxury crap for off-roading not to mention there aren't that many aftermarket providers for these types of components to begin with.
It mostly comes down to the fact that larger vehicles aren't as good for off-roading and the Sequoia and LC100/LC200 are still a bit more expensive than getting a used 4Runner. Also most of the people who gravitate to those vehicles are not looking for an off-road toy, they want a cushy mall crawler or "manvan."
The 4Runner has typically offered a great medium between creature comforts and off-road capability in a relatively comfortable package that lives well in day to day living while having the capability and strength off-road to wheel them hard. In this case the 4Runners tend to be in that "not too cheap, not too ritzy, and just the right size" category that checks a lot of boxes for people looking for a daily driver and/or off-road warrior. Part of the reason I bought my 4th gen was because the 4Runner ended up being the best mid-sized SUV for my needs in both off-road, utility, and daily driving.