Perdid, it does make sense why they created Fongi out of thin air.

Marvel isn't keeping Jean dead.  Not really.  There may not be currently a character called Jean Grey in the books, but they have given her power (the Phoenix), her attitude and relationships (fiery red head who argues with Emma Frost and who asks Wolverine to kill her if need be), and now apparently to Fongi . So that means the concept of Jean Grey/Phoenix is so strong Marvel cannot help but use it, while they officially keep Jean Grey dead.  And that's what has Jean Grey fans so upset, if there were truly no Jean stories to tell, why make Hope look like Jean, dress in green and gold like Jean, hate Emma like Jean, want Wolverine to stab her like Jean, etc?  Clearly there are Jean stories to tell, they're just telling them and calling her Hope, or maybe Fongi now.

Marvel talks about keeping the dead/dead, but either they resurrect them, or they create a character so similar its a defacto resurrection.  Mastermind, a malicious telepathic illusionist dies, but it so conveniently turns out he has two daughters, Mastermind and Lady Mastermind, who are equally malicious telepathich illusionists like their father, who inherit their father's hatred of the X-Men, and even join teams like the Brotherhood of Mutants, the Sisterhood of Mutants, alliances with Sebastian Shaw, all like their father would have.  So it means Mastermind isn't dead, his powers, his attitude, and his motivations live on in Marvel through his daughters.