I'm someone who can't grasp standard. I don't get why he's so strong. Is it the synergy with other cards in the current standard?
Edit; I mean to say current standard
Few reasons really
Hes a 3 mana planeswalker who comes down on turn 2-3 and immediately goes to 6 loyalty,
Pretty much any deck will struggle to deal 6 damage to him on turn 3 so hes survivable
Then you get to what he actually does
Against aggro they either waste a turn and some number of spells to kill him buying you time *the most important resource* in order to get to your stablising krasis, or they ignore him and you get to make a 3/3 every second turn who will be bigger than any creature the aggro deck pull out outside of runaway steamkin, the red legendary dawrf and they phoenix, all of whom oko can turn into a 3/3 himself.
he turns your opponents best creature into a 3/3 with no abilities, standard is full of mid range decks that function of the abilities of their creatures, adventure decks are just full of average creatures if your not drawing cards off of inkeeper, aristocrats decks are just a bunch of 1/2s without their sacrifice and dies triggers. etc etc
they also printed a cycle of mythic artifacts that are pretty unplayable (embercleave probably being the sole exception as at least you get a single turn of use from it before it becomes an elk)
and in the control match up he literally just makes a 3/3 every second turn for free.
very rarely do you have a card in standard thats in your top 2-3 cards in your entire deck in your aggro, mid range and control match ups.
But they managed to do that here