Wakandans chose to hide from the world rather than conquer it because they wanted to protect their advanced technology and resources from outsiders who might seek to exploit or misuse them.
Wakanda is portrayed as a highly advanced and prosperous African nation, thanks to the presence of Vibranium, a rare and powerful metal that is unique to the Wakandan region. The Wakandans are able to use Vibranium to create highly advanced technology, such as advanced weapons and medical devices, that far surpasses anything else in the world.
However, the Wakandans recognize that their wealth and power would make them a target for outside forces, who might seek to invade or exploit their resources. They also recognize that their society is unique and precious, and they do not want it to be contaminated or corrupted by outside influences.
Therefore, the Wakandans choose to remain hidden from the world, and to carefully control the access that outsiders have to their resources and technology. They use advanced cloaking technology to conceal their country from outsiders, and they carefully monitor all interactions with the outside world to prevent any breaches of their security.
While some Wakandans, such as T'Challa (the Black Panther), eventually come to recognize the importance of engaging with the outside world and sharing their resources with others, the initial decision to hide was made in order to protect their people and their way of life from outside threats.