Fracking has been tried on and off for decades but it was only recently that wildcatters struck upon the right formula and techniques to unlock the Bakken.
Horizontal drilling is key in this region because the Bakken is like an oreo cookie: a thin layer of crude sandwiched between two huge layers of rock. Fracking breaks up the small inner layer while horizontal drilling lets a single well drill down into that layer and then within that layer, unlocking far more crude than with regular vertical drilling.
What was needed was not technology, but oil prices over $80 per barrel.
At least that's what someone who does this for living said.
Moreover, fracking came in to vogue due to drilling for natural gas, not crude.
Also natural gas is WAY cheaper now that it was 5 years ago. Its so cheap that a lot of oil companies are voluntarily not pumping out of some good wells because they want to decrease supply.