What If Crisis Happened Differently in 1986?

From Amazing World of DC #12: “The pivotal time will be October, 1986... and in that month, the future of the world will be decided. Either the path of the Great Disaster will be taken, and civilization will fall, or the path of sanity will prevail and the Legion of Super-Heroes will emerge triumphant a thousand years later. Until that moment… two alternate futures of the DC universe… chronicled in a different set of magazines.”

“SUPERMAN #295 established the essential crossroad: a Green Lantern of the future came to 1975 to insure that the dual timelines might develop without outside interference. He explained the concept of alternate, parallel futures each of which exists and is real, born of a single critical decision somewhere in human history.”

“The next few years are safe scientific progress will take place, civilization will grow more stable, and the society chronicled in OMAC will emerge. This is the society which may fall in World War Three, and whose descendants will suffer the Great Disaster. But if World War Three does not take place at that time, then generations later the Legion will appear.” 

What developed was a war between the Olympians and the forces of Darkseid from the planet Apokolips. The resulting conflict would spill over into Earth-One, causing the Great Disaster from this third World War, causing animals to mutate into intelligent entities. This would be the alternate future reality known as Earth-AD in which seemingly ordinary Buddy Blank became its superhuman protector, Omac (One-Man Army Corps), powered by a sentient satellite known as Brother Eye. 

When that Eye originally was destroyed, Blank returned to normal and ended up raising his grandson in a bunker known as Command D. Losing his life to protect his descendant, that grandson continued his heroic legacy, becoming the youth known as Kamandi. In the main timeline, the boy grew up and was raised by General Horatio Tomorrow, and became the ace Planeteer named Tommy Tomorrow. Other potential future inhabitants included the Atomic Knights, while Wonder Woman's Amazonian sisters remained shielded from the Disaster by moving to an alternate dimension.

When the aforementioned Green Lantern from a thousand years in the future disguised himself as the villainous Father Time*, he sent Superman into his era but in the Great Disaster timeline. Battling a future champion with powers like his, Superman and his opponent unleashed enough energy to revert the timelines into two separate futures. 

It was revealed by "Father Time" that the evil Time Trapper* manipulated energy from the future Green Lantern Corps in order to eliminate the 30th century prime timeline, thereby erasing from existence his old foes the Legion of Super-Heroes. With that future now restored, it once more became the Earth-One unaffected by either the Great Disaster of Earth-AD or the Crisis on Infinite Earths, both of which occurred in two distinct futures.

However, Sergeant Gardner Grayle was inserted into a virtual reality experiment by S.T.A.R. Labs, which inadvertently created a replica of life after the Great Disaster, mirroring events similar to those experience in the Earth-AD timeline. Superman helped to reverse this experiment, freeing Grayle and other individuals within this virtual reality.

While this occurred, the future of Earth-Two and other parallel Earths had their own distinct branching futures. On Earth-Two, one future spawned the Space Legion, Brane Taylor aka Batman and the Defenders of its prime 30th century, and the divergent future Earth-2A in which the champion known as Gary Concord the Ultra-Man and his similarly named son resided.

* The Father Time of Earth-Two was a disgruntled intellectual who came into possession of a mysterious "time scythe" which alters the molecular composition of cells. The villain used this for common thefts, until he and his gang were brought to justice by the Justice Society honorary member Wildcat.  

** Time Trapper's Earth-Two counterpart, Doctor Doome, had ventured into the future following his defeat at the hands of Law's Legionnaires, and used his time machine to escape capture. It is unknown if his influence somehow created the branching future timeline of Earth-Two-A, although this is a distinct possibility.