The slashes were big because of racing.
Really if people didn't race them I don't think there would have been as many sold. Think about that, why whould a race company make a truck if there wasn't a fair sized race program going on for the class (AE has never started trends, instead they like to do what is big on the track when they come out with a new car (hence most of their cars are top of the line race cars)).
AE came out with a race version truck, but at the same time like traxxas used many parts that they had laying around the shop so that is why it is more of a race truck, as it is based off of the T4. The slash was based off of a rustler (I think) so both use what they had with to an extent a differnt chassis.
The losi in no way can race, as it is not legal for racing for the roar SC class. Also it wouldn't be ran in the slash spec class as that is a slash only class.
Ok for bashing only (as that is all it is able to do as it isn't legal for racing), but that is going to hurt sales as you can't truly race it, and the fact that it has a relabled traxxas motor doesn't mean it will race with the slashes.
Also AE didn't go off of what slash racing is about, but because of the fact that it is just a longer T4 then that means that it will out drive the slash. But I don't think that is what is killing the class, as I think it is pro-line and jconcepts as they have tires that are no longer low grip shoes, instead they have tires that are made of their soft compounds and are based off of their race tires. So if you want to race say the SC10 then it will be in the roar sc class, with a 17.5 BL motor, etc., and is also where the losi will have to race in.
A spec class is where only 1 chassis, 1 motor, 1 tire, and in some case 1 type of battery is used (some places leave it somewhat open, and others make you run a cheap stick pack ni-mh), and there is normaly only set-up changes allowed for the car. So with that in mind losi doesn't have a clue anymore as you can't make a car to race in a spec class as the spec class is only for the slash, and it is unlikely that there will be a losi spec class as not that many people are a losi fan, so if they were smart they should have made a car that was legal for the sc class, but hey hirozen has been running the losi name into the ground so good for them for a failure.
There are some of my thoughts as to what I think.
Also lug the X6 is the mid motor conversion for the B4 that is made by X-factory, and the X-60 is the mid motor T4 (yes they have a truck now to), and their other car is the X-5 that is the XX-4 (one of the best 4wd cars for a rough track), and the xxx-4. Also on a side note the owner did some annoucing at a race that I went to a few months ago durring the mains.