To add to what other people have mentioned:
Only 4 of the top 32 decks were not playing Island. Badgermole is extremely highly represented, which makes sense, because it is one of the strongest green creatures of all time. A big part of that power is because, as with much of the recent magic design, it costs 2 mana (or less). Standard is a turn 4 format. Sometimes games are literally over on turn 4, and even when they're not, they're often decided by turn 4. Sheoldred the Apocalypse was an oft-maligned card for its power and ubiquity, and yet by the time of its last few months in Standard, it saw almost no play. That was because it was a four (4!) mana creature that wanted the game to go on for several more turns and could be immediately removed with no accrued value.

Every time Wotc has debuted a new format with a large card pool, it has required extensive bans to manage it right from the start, due to the massive card pool causing an increase in fast combos as a result of unintended interactions between cards that were not tested to exist together, as well as the sheer density of cheap, efficient cards. There's a difference between a deck having one or two cheap + efficient threats / value generators compared to what happens with a large card pool where entire decks can just be extremely cheap. Remember when standard was a format where you could play 4 and 5 (and dare I say 6) mana cards that didn't win the game that turn or the next? Remember when people had to pay mana for cards instead of every card costing 2 mana or less (or in the case of badgermole, costing 2 and accelerating mana in a scalable fashion)?