There just aren't that many Vehicles in the game, since the subtype Vehicle was introduced in Kaladesh in 2016
As more and more creatures with enter the battlefield effects, low costed high toughness, or mana taxing abilities have been printed, the one-for-one trade that Lightning Bolt offers has become less and less appealing
These are all things that synergize with greens general strategies, so you arent stuck building an elf deck if you want it as your commander
If youre new to Commander or want a refresher on the basics, check out our guide on how to play MTG/Magic: The Gathering before diving into this deck
Because you cast whatever creatures Azula swipes, you don't need to worry about giving it back if your opponent removes Azula like you would with Mind Control variants, and the enters ability means your opponents are always two-for-one'd at best