They say to keep your friends close and your enemies closer – but what do you do when the enemy is your own brother?
This is the unknown dilemma actually faced by Mario. Not content with living in his brother's shadow, Luigi took to a life of crime by becoming the faceless underworld kingpin known as Master Hand, with one sole purpose: to make his brother's life a misery and bask in the glory.
Besotted with Princess Peach but unable to woo her, tired of Mario being the face of the company and while he would get sent on ghost hunting missions, Mario was showing Peach his own Mushroom Kingdom. It was time for change and how better to instigate this by being the person least expected to cause trouble.
Let's look at the facts, Luigi had Mario's trust, quiet and unassuming, he was the perfect confidante – he could know Mario and Peach's whereabouts at all times – ideal for when a kidnapping needed to take place.
As the Master Hand, Luigi had control over all the scum and villainy the Mushroom Kingdom and beyond had to offer. Wielding them to do his bidding whilst rewarding them for their loyalty even in the face of inevitable defeat. The aim was never to defeat his brother, merely prolong his suffering, allowing him a victory here and there only to strike back doubly hard the next time.
Hoping that the weight of never ridding the world of Bowser, the Koopalings, Wario, Waluigi or any enemies for that matter, would eventually crush his brother's spirit allowing him to rush in and defeat them all in one fell swoop; doing what his brother never could. Luigi would not only be the hero, but also the enemy, orchestrating his rise and stay at the top all at the expense of his brother.
You can't choose family, unfortunately for Mario.