The reason for the Chaos Orbs illegality is the rather bizarre way its played onto the table
Since you can repeatedly cast it from your graveyard at the small cost of just two life, Tenacious Underdog is a reliable creature and draw engine for multiple decks in Standard
Diabolic Tutor 7
The new expansion is part of the Genetic Apex umbrella, much like how the Pikachu, Charizard and Mewtwo boosters all have their own card lists and drop rates
To counteract this there is a mechanic called Banish that is like sending a card to the graveyard, but in this case, it is removed from the game period
But I dont think cards like this should ever existregardless of how hard the hoop is to jump through, Thassas Oracle is just too inexpensive and too acceptable on its own for a card that says you win the game. I think Thassas Oracle is a consequence of three things: Jace, Wielder of Mysteries blurring the lines of whats acceptable, a dictate to power up cards (including ones that normally wouldnt be meant for Standard), and a loss of institutional knowledge within Play Design about effects to be extra cautious about
