It is popular because of the tremendous board control it brings backed up with hand destruction and recursion
Palladia-Mors, the Ruiner has a lot of keywords attached to a fairly large body
You have to pay the equip cost to attach the equipment to a different creature, which unequips it from the creature it was originally attached to
From the outset, players have struggled to clearly identify what exactly appears in any given Collector Booster
While Rakdos Charm lets you kill an opponent thats gone too wide, or blow up an Aetherflux Reservoir at the right time, it has also had a lot of success as a flexible role player
This lets you know in advance what cards you need to Pithing Needle, what you need to set Chalice of the Void to, and how aggressively you need to find Welding Jars