why did it bomb?
-XM Apocalypse disappointed critically and with audiences (usually when that happens the next movie suffers at the box office - e.g. BvS-JL)
-Logan seemed to wrap everything up nicely (if that's the right word) closed the book on the Xmen. so this with the younger cast/no Wolverine (first time) and going back to the 90s seemed abit redundant (and didn't even seem necessary as theyd completed their trilogy – so 3 X trilogies - original cast / Wolverine / younger cast)
-average moviegoers who aren't crazy lap up everything superhero have already seen this story with the original cast back in 2006 or on DVD/blu/streaming/regular tv since and had little interest in seeing an even more poorly reviewed version with a younger cast/no Wolverine.
-Endgame made everything coming after seem 'small' in comparison to moviegoers even Godzilla and especially a similar 'Endgame' 4th team up/finale marvel superhero film (that dealt with a cosmic threat) that wasn't really necessary in the first place (ever since Avengers MCU has been slowly eating up Xmens audience culminating in the Endgame annihilation). the original Nov 18 or Feb 19 release dates would've at least avoided coming after EG (but then XM has always been summer) actually this summer is turning out abit like 2016 everything aside Avengers underperformed (Xmen, Star Trek, turtles, ID2, GB, Tarzan, Alice2)
-oversaturation of superheroes. in past 3-4 months audiences have had Cap Marvel/Endgame/Shazam/Hellboy.and now an unappealing looking Xmen...so obviously some are going to get lost in the deluge esp after the one two punch of MCUs CM/EG...now audiences probably just waiting until Spiderman HC 2 for another MCU fix
-think moviegoers still consider the original cast the 'proper' XMen and these younger versions as like the pretend fakey ones (abit like JJs Star Trek although at least with Trek they had to recast if they wanted to use the original characters) and especially coming after the subpar Apocalypse (which was boosted by the near Avengers level event of DOFP featuring both casts - which made it pretty much 'XMen 4' with the original cast)
-the Disney/MCU takeover. MCU is now all powerful and everything is in its shade and its made the Fox XMen seem like its now redundant (although maybe only the geeks would be aware of that.. but then again everyone abit of a geek now/knows about MCU and is aware of that behind the scenes rights stuff) - actually could this be the 1st time ever that a franchise film series has had a reboot announced before/during the current films release?
-The Bryan Singer connection - ever since the BS allegations its cast abit of a cloud over the X universe he created (although it didn't do Boh Rhap any harm lol)
-The bad reviews/low RT score (especially coming after the critically acclaimed all powerful Endgame)
-dull/'seen it all before done better' looking trailers