He planned to lie about Cooper's death being an accident and later on, tactfully introduce the idea of colonizing Edmund's planet instead, since conditions were more favorable for human life, and the Endurance was available for the journey.
Mann is an example of humanity's selfish nature – his surname is a not-particularly-subtle bit of signposting – as he deliberately manipulates his data to pretend that his ammonia-filled planet is habitable. He sabotages Coop's crew purely to escape from the planet and make it back to Earth.
On his deathbed, Professor Brand confesses to Murph that he lied about his Plan A's prospects – that he failed to “reconcile relativity to quantum mechanics” and his gravity project needs much more data. She takes on the project herself and beams out the bad news to space, where Coop and Amelia receive it.
Dr. Mann, driven to madness from being denied basic human contact, convinced himself he could lie and murder for the sake of the survival of the human species.
Why did Dr. Mann fake the data about his planet in Interstellar?
They awaken Mann from cryostasis, and he fills them with the hope that the planet he discovered could support human life. However, he privately reveals to Cooper that this is a lie. He falsified the data so that NASA would send a crew to rescue him.
Mann finally went through with his survival intentions: to fake his planet's data from hypothetical models from his robot KIPP, booby trapping KIPP, and put it in a more optimal perspective, and to be a leader on humanity's new planet.
It is then revealed that he and Professor Brand knew that Plan A was impossible and that the only contingency that allowed for human continuity was Plan B. Mann did not want Cooper to return to Earth with the Endurance, as he now needed it to reach Edmunds' planet with the remaining crew to start a colony.
Mann explains that he had to decommission the robot because it began to malfunction by misidentifying organic life as ammonia. We soon learn that the robot correctly identified the absence of organic life on the planet, and its insistence on not sending back a false message resulted in Dr.
Through Dr. Mann says, “I'm here for you,” while Cooper dies, Mann can't tolerate the suffering and turns off the speaker in his helmet. At this point, the film cuts to Murph turning her jeep into the family cornfield, where she will set fire to the corn in order to force Tom to leave.
TARS relays the quantum data to Cooper in Morse code. Cooper in turn relays the quantum data to Murph, in Morse code, through the hands of a wrist watch. Murph somehow knows it's her father relaying quantum data to her through the watch.
It took the spaceship 18 months to travel to the wormhole, then 23 years passed from exploring planet Miller. Murph said (cried) in the video to his dad that she is finally the same age as him when he left. Which tells us that she and her dad are both 35 years old toward the end of the movie.
The ending is by far the saddest scene. Cooper visits Murph in the hospital when she is old and dying, and they have a moment together. Very likely to make viewers cry. A character driven mad by isolation tries to kill another character, but fails.
Finally, one this to note is that for the transcript for Interstellar, Dr. Mann's last words are, 'Brand, I don't know what Cooper's told you, but I'm taking control of the Endurance, then we'll talk about continuing the mission. This is not my survival, or Cooper's - this is mankind's- '.
Mann faked data about his planet's viability so Endurance would rescue him. Mann breaks Cooper's spacesuit visor and leaves him to die, and flees to Endurance on a shuttle; Romilly is killed by a bomb Mann set to protect his secret.
Upon arrival on Mann, the eponymous doctor had KIPP conduct much of the ground exploration of the planet's surface. Dr. Mann subsequently dismantled KIPP, booby-trapped his mainframe and used his power cell for the energy of his hypersleep chamber.
He cannibalized KIPP, using its power-source for extra energy for his hypersleep chamber, while rigging the robot to explode if someone attempted to access its archives - which would unveil the truth about his world. When the Endurance crew arrive, they awaken Dr. Mann, who convinces them that his world is habitable.
Mann realizes his planet was uninhabitable. He dropped probes at nearby locations with the hope of finding a rocky, habitable surface, below the frozen clouds they stood on. After years of probing and exploration, he found no surface.
After finding his planet's conditions to be promising for human life, Edmunds sent a "thumbs up" signal back to NASA on Earth. He subsequently settled into hypersleep and awaited to be rescued. During this time, a rockslide occurred and destroyed his landing pod, causing Edmunds' death.
Brand was alive, starting the plan B alone somewhere. All Murphy knows is that Cooper somehow sent messages to her. Since she completed the equation, she can infer Cooper saw what's beyond the Event Horizon. She can also infer he most likely fell into the black hole.
The spaceship Endurance's destination is Gargantua, a fictional supermassive black hole with a mass 100 million times that of the sun. It lies 10 billion light-years from Earth and is orbited by several planets. Gargantua rotates at an astounding 99.8 percent of the speed of light.
On Mann, Romilly was killed in an explosion caused by Dr. Mann while accessing KIPP's archive; which contained the true data of the planet. TARS escaped the explosion and was able to rejoin the rest of the crew in the lander.
Romilly didn't sleep for the whole period, that's why he looked aged compared to Cooper and Amelia when they come back. He was a scientist by heart so after taking a couple of stretches as he said, he started doing research on the black hole (Gargantua) and that's how he spent 23 years.
Murph tries to reason with Tom, but he refuses to budge. Meanwhile, Cooper realizes that Mann faked all of his data, that there's no habitable surface on the planet. Mann concedes that this is true, that he sent out his “thumbs up” signal only so that he would be rescued, and that he knows he's a coward.
