I see X-Men as the Savior of Marvel Comics. And Marvel and their fans have turned their back on X-Men.
X-Men had the highest viewed cartoon for Marvel
Sold 8.1 million copies of X-Men #1
Created the crossover fighting genre
X-Men Movies enough said
Every time a Marvel game out it was X-Men first
(Children of the Atom then Marvel Super Heroes, Mutant Apocalypse then Marvel War of Gems, X-Men vs Street Fighter then Marvel vs Street Fighter etc etc)
Marvel has kicked X-Men to the curb no action figures barely 4 comics a month when I use to get over 20 X books a month.
To be fair... it's incredibly common for a property to also go out of popularity...
Cap was huge in the 40s but had no place in the 50s so took a back seat until the Avengers brought him back in the 60s
The Fantastic 4 were huge from the 60s until the 90s and then went on a steady decline
Hulk was huge in the 70s and then declined in the 90s only to become popular again once the mcu put him back in
The Avengers were pretty big in the 60s and 70s but sat out most of the 80s and 90s before the mcu
The xmen were not really big until the late 80s 90s... but have struggled a bit since. Especially in the books.. and it has little to do with marvel choosing anything... they're in the business to actually make money... they arnt going to half@%& a property for no reason. The only x-property to really grow to 90s proportions has been deadpool
That all being said... you are aware "everything" can't be popular at once... and a company can't put focus onto everything at once either... it's a bit ignorant and arrogant to assume marvel as a company should spend less time focusing off of popular brands created by the films they own and that fuels the entire brand... to instead focus on a brand they do not have as much stake in...
The xmen are not the biggest brand under the sun anymore... and it's honestly no wonder why... the xmen movies really haven't been age inclusive they arnt films both kids teens and adults enjoy.. they also tend to lack humor and a sense of fun, in favor for deep dark and serious genocidal stories. That doesn't appeal to a younger audience.
It's no secret movies are the biggest form of advertising and hype. This is what also sells merchandise... and the largest portions of merchandising is what mass retail buys into and deems "worthy" they sorta also control everything... movies sell merch and merch helps sell the film in return as well basically snowballing the brand.
The xmen films (and fantastic four) spun toy lines that unfortunately peg warmed (didn't sell and kept product longer in stores than stores wanted) the most notorious being the x-men origins and x-men 3 characters who were in 2 packs and part of the Marvel legends line. Stores bought a bunch because of the xmen brand (they care about a brand title not movie vs comic) and thus for subsequent years severely limited their inventory. The black leather costumes were not appealing to children
Hasbro had such a hard time trying to find a home for the wolverine legends wave they scrapped 2 figures from it and had to make it an online/specialty store exclusive. The xmen legends wave with a build a figure jubilee (and had very heavy hitters like Cyke, Magneto, wolverine and storm) also were forced into being retail exclusive (toys r us)
Luckily though the wave that is comic based, and comes out this summer is mass retail for the first time in a long time... so that's a great sign things are turning around (as long as they sell well)
When the disney/marvel purchase happened it unfortunately canceled some great things.. like wolverine and the xmen and avengers earth mightiest... Disney can only do so many animated shows at once... there's just not enough space in programming and animation studios they work with to go around... and it's incredibly logical that they want to continue the brand promotion on properties they do have a big stake in.. so you can't really fault them for that...
The bright side is... sometimes properties simply need a break (which the fantastic 4 are doing now above everything else) in order to rest, disappear, and then get people missing them. So they can make a big return better than ever.
Which I can easily see happening if Apocalypse turns out to be a really fantastic film and mass retail will also view the property as very viable if the xmen legends wave of figures is very successful...
I'm ordering a case of that wave to ensure I even get it... it's highly anticipated among fans... and includes figures of (cable, Deadpool, iceman, Phoenix, Havok, kitty pride, and rogue with juggernaut rumored to be the baf) it's no secret those are all pretty big names... Hasbro wants the line to sell just as much as everyone else.... so hopefully it does... that combined with the film could easily make the property popular again.