[paulpauper]

The power 9 became so powerful when later on it became possible to make combo decks that could win within 5 turns

[empath75]

There was a black lotus first turn kill in the original set:

Black lotus, mountain, channel, fireball.

And you could make a deck with 10 of each of those if you wanted according to the original rules.

[rcxdude]

5 turns is slow for any constructed format which includes the original sets. (heck, I've pulled off faster combos in a vintage cube draft)