I think that all the factors you've mentioned are correct:
- The plastic kits have been few and far between, both in 1/72 (the scale I do) and 1/35. And resin kits are hard to get for the average modeller. WW2 kits, on the other hand, are very plentiful!
- Info on the hardware, both regarding the pure technical side, and camouflage and markings, have been very hard to get. On the other hand, info on the same matters regarding WW2 have been very easy to get!
Then WW2 is a conflict that lingers in peoples minds in another way than WW1. Especially in the US. (I've once heard a young american saying: "All say World War Two. Does this mean that here also was a World War One?") WW1 was much more of a European conflict, and a deeply tragic one for that. There is little of the aura of heroism that still stick to WW2. (No cool Waffen SS-ers there either.) It was not, regardless of how you cut it, "A Good War".
But WW1 Military Modelling is slowly growing.
And I don't think it's a lost cause. I think you can draw a parallell to WW1 Aviation Modelling, which is now very strong, with super kits coming out, and large enough to support both a magazine (Windsock) and a steadily growing body of excellent literature.
And I think that the thing that draws people to WW1 Aviation also can draw people to WW1 Military subjects, like strange, exotic and even funny shapes, like colourful markings and camouflage. And WW1 Military modelling will sooner or later reach a "tipping point", when it becomes as big as, say, WW1 Aero Modelling. And this development will be a result of
- The market seeing more and more plastic kits. There are already signs of this: RPMs differents WW1 kits, Mirage and HäT soon to do the FT17, The EMHAR Whippet, following pretty soon on their A7V (both very good BTW). And if you go to the resin market, you can already find almost everything! At least if you do 1/72
- Info on harware, camo and markings being easier to get. There are positive signs here as well. The last year has seen several good book on WW1 Tanks and Arty coming out. And just recently Osprey has released or is about to release several on WW1-era hardware - and their thumbs usually seem to be pretty well up in the air... (And I would like, in all modesty, like to recommend my own site, http://www.landships.freeservers.com
started just because of the lack of good info for the WW1 Military Modeller)
- And now, if a crack modeller like MIG will do some WW1 work, well, then I'm sure the sky is the limit!
Because this is off course important as well, with ace modellers showing what can REALLY be done!
All the best