These reasons include the card's rarity, popularity, age, and design
What makes him very strong is his metalcraft to equip for free all day long if you control at least three artifacts, which is so easy since it counts lands and tokens, and with the card draw combined with that free equipping, he is an Equipment essential
Since it comes back in the end phase, it's not very reliable as a wall, but on the contrary, it's strong against removal, and it's easy to connect with Synchro or Xyz
These combinations and more await in the world of Creature-type matter decks
Onto Age Of Sigmar, we got three fantastic cards out of the gate
It usually takes multiple cards to get rid of the Dragon, so it gets tougher and tougher to stop with every card the opponent loses