The salvation of all is guaranteed by the death and resurrection of Christ.
But some don’t acknowledge that there are eons of time in “God’s eonian purpose” (See Eph 3:11)… and during the eons some, like those who did not enter Noah’s ark… do not see life.
But what happens during the eons is not the same things as what happens when the eons are complete.
Eonian life is for a few.
Eonian life is not the only thing Christ accomplished at the cross on our behalf.
Eonian life is for believers among the nations.
Eonian life is for those of Israel who keep the law.
God is especially the savior of believers.
But God IS the savior of all.
Not all believe… but all for whom Christ died will see life, and he died for all.