There are a ton of ways to maximize the mana generation of this card (cough elves), and the massive mana income you get from Gaeas Cradle can be used to fuel your swarm or to bring out big spells or giant monsters that green loves so much
Many hove strong abilities that generate value by creating creature tokens and/or directly helping crew more vehicles (Shorikai, Parhelion, Peacewalker, etc), draw cards, deal direct damage, accelerate your mana, and more
Sure, its squishy as an 0/1 for three mana, but is anyone really excited about wasting a removal spell on it compared to other, more scary creatures Ill have on the battlefield
I give a huge nod to Hakoda for covering indestructible's big weakness to -1/-1 effects with the +5 toughness
The persist ability makes combat complicated for your opponent here since anything that survives on your field can pick off anything that survived on theirs