PARK CITY, Utah — It was the independent film equivalent of a crack of thunder.

After its Sundance premiere on Saturday, “Manchester by the Sea,” a buzzy drama starring Casey Affleck as a handyman coping with family strife, sold not to a traditional studio distributor but to a streaming service. Amazon paid a hefty $10 million for the movie, beating out the likes of Fox and Universal.

After years of dipping their toes into the Sundance water — picking up a documentary here, making an unsuccessful bid for a narrative film there — the big streaming services this time around are driving the deal-making. Halfway through the 11-day festival, which started on Thursday, Amazon had bought four films. Netflix had snapped up three and was chasing several more. Most traditional distributors had yet to buy anything.

“We’re interested in distinctive films by artists who have something new and interesting to say,” said Roy Price, head of Amazon Studios.

The streaming service shopping spree does not just reflect the ability of these deep-pocketed insurgents to outspend the entrenched studios. Filmmakers, once dismissive of streaming companies, have been looking at the struggling art-house box office and deciding that getting their work seen by the widest possible audience — while being handsomely paid, of course — may be what matters most.