Vyram, simply put, debuts the series with backstabbing and exits the series with backstabbing.
Cooperation between members was barely - if at all - existing, mutual contempt and distrust were rampant within the upper hierarchy staffs, and they had no loyalty towards their empress whom they served. The core members who are commanders of the group possess way too much pride for their own good, and often their enmity towards each other gets in the way of their mission.
When a member fails to kill Jetmen, words of comfort was impossible to expect as the failure is subject to endure all manners of intolerable mockeries, insults and humiliations from other members. Because Empress Juuza was wounded during their last dimensional conquest, she was forced to hide and recuperate, leaving the Vyram's leadership in vacuum. The remaining Vyram members, opportunistically exploiting this vacancy in leadership, took it upon themselves that whomever conquers Earth first would be the next leader of Vyram. So Vyram members attempt to conquer Earth in a bid to compete for the leadership title - as if they are playing a contest. And when Juuza did return after healing herself, instead of rallying behind their mistress and supporting her the remaining members schemed to overthrew Juuza (involving Jetmen) which ended with her demise.
Regrettably on Vyram's part, its members had some crucial chances to destroy Jetmen, especially on early arcs of the series - as Jetmen in the beginning were disorganized and incoherent ragtag band (a soldier, a criminal, a young teenager and a spoiled rich brat etc.) with two of its strongest members constantly at loggerheads with each other, often forcing its commander to physically intervene to keep the peace between Jetmen members. But with uncooperative nature prevalent amongst Vyram members, they were not able to exploit these potentially decisive chances effectively. Later Tranza almost succeeded in destroying Jetmen, only to be thwarted by traitorous Radiguet.
While Jetmen played a significant role in defeating Vyram, Vyram members' infighting was no less vital in playing its downfall. Vyram's members were their own worst enemies.
After having conquered many worlds in the Back Dimension, the Vyram used their Dimensional Traveler Machine to invade the Front Dimension and attempted to conquer Earth. Vyram members hold people of Earth with nothing but contempt, calling Earthlings as "silly beings". As their leader, Empress Juuza, was missing in action, the four generals of the Vyram competed against each other to see who could conquer Earth in order to decide who would be leader.
Empress Juuza later returned to lead the Vyram and hatched a scheme to awaken her ultimate Beast, Semimaru, by feeding it human suffering. However, she was defeated by the Jetmen with help from a traitorous Radiguet and the Vyram were left leaderless once more.
Tran later briefly seized control of the Vyram after becoming Emperor Tranza and banishing Radiguet, but he too was defeated by the Jetmen, allowing Radiguet to come in and take full control of the Vyram for his ultimate scheme. Ultimately, he too was defeated and with most of the Vyram commanders having also been taken care of, the Vyram became no more.