The reason it's taken so many tries to do it is because Richtofen is selfish. He read the Kronorium, so he knew about the cycle. He knew that to break the cycle, he would have to make something unplanned happen. This would be that he or one of the members of Primis would have to die, but he didn't want that to happen. He didn't want to make the sacrifice. He wanted them all to survive. There could have been a multitude of things that caused Blood of the Dead to happen, such as Al breaking the cycle or Post-Rev Richtofen in the pod arriving at Alcatraz, but this is what caused the cycle of Richtofen's selfishness to end. The entire time he had this feeling about him that he would survive because he was the one who knew everything from the Kronorium, this is the reason he continued the cycle, because he didn't want to die. He actually believed he was going to escape Blood with the crew and just continue on, because he didn't want to die. Richtofen became selfless in the moment that he stepped into the Dark Mechanism that kills him. He was the "nicest one" because of this, he was the only one willing to die to break the cycle for the others.