Mike Hopkins’ departure Tuesday from his post as CEO of Hulu to become chairman of Sony Pictures Television was a surprise. It comes just as Hulu appears to be having its moment. In September, the company became the first streaming service to win a best drama-series Emmy with “The Handmaid’s Tale,” and earlier this summer it jumped into the skinny-bundle fray with a much-hyped live-TV offering.

Sony, meanwhile, looks like a dogsbody of a job. Still recovering from the morale-shattering 2014 hack and a draining executive exodus, the company is in rebuilding mode under respected former Fox TV exec Tony Vinciquerra. But the television studio faces enormous challenges in a marketplace where vertical integration is a top priority and SPT has no sibling network to funnel product to. When the upfront dust settled in May, SPT had sold three broadcast series, fewer than any other Big Six studio this season. All are co-productions. On the positive side, Sony TV is behind the breakout show of the season so far, ABC’s medical procedural “The Good Doctor.”

Hopkins will be replaced at Hulu by Randy Freer, COO of Fox Networks Group, one of Hulu’s owners. The CEO handoff seems to come at an odd time but there are several potential explanations for the shuffle.

1. Mission Accomplished. The most positive take is that Hopkins accomplished all his goals at Hulu, successfully launching the live-TV property, beating Netflix to the Emmy, and even hiring a top-flight content executive in Joel Stillerman, who joined the company from AMC earlier this year, to guide original-series programming for years to come. Having reached the summit, Hopkins gazed out at the landscape and spotted an even more challenging mountain to climb — Sony Pictures Television.

It is tough to argue that there isn’t some merit to this view. Hopkins’ departure feels odd precisely because Hulu has enjoyed such positive press on the heels of the “Handmaid’s” Emmy run. From an original-programming standpoint, Hulu appears to be moving past its growing pains and capturing elusive (and difficult to quantify for a streaming service) buzz. It has also established a programming identity as embodied by “Handmaid’s” and summed up by senior VP of content Craig Erwich when he spoke to Variety in September after the Emmys: “We’re looking to tell intimate character stories against large worlds and large canvases that have really strong, resonant, and permanent dramatic underpinnings.”

2. Don’t Look Under the Hood. A less charitable read is that the awards success of “Handmaid’s” masks fundamental challenges to Hulu’s business even more daunting than those faced by SPT. Hulu last reported it number of domestic subscribers as 12 million in 2016 — a number that pales in comparison to the 53 million that Netflix reported last quarter, and far fewer than the number of cross-platform subscribers on premium linear channels-turned-streamers such as HBO, Showtime, and Starz. Without any significant international presence, Hulu lacks the same growth potential that Netflix and Amazon enjoy. And as a partnership of four media companies — The Walt Disney Co., 21st Century Fox, Comcast, and Time Warner — it lacks the full commitment from any one corporate parent that, say, CBS showed when it committed to putting “Star Trek: Discovery” on nascent over-the-top service All Access.

And Hulu’s big bet on live TV has yet to pay off. Digital MVPDs have proliferated, with offering from DirecTV, Dish, Sony, YouTube crowding the marketplace. But although subscriber numbers for individual services are scant, analysts have pegged the total number of digital MVPD subs in the low seven-figure range — not large enough to pose a real threat yet to traditional MVPDs.

3. View From the Top. Feeling the pressure from Netflix, Disney CEO Bob Iger announced in August that the company would launch its own entertainment streaming service in 2019. Disney pulled out of its feature-film output deal with Netflix, and plans to move its movies — including those produced by Marvel and Lucasfilm — to its new service. In addition, Disney-ABC Television is expected to produce original series for the new platform, and push existing series in their post-broadcast windows there as well. “You have to think of the Disney app as a traditional SVOD service,” Iger told investors in September.

With Disney building a wholly owned service, does it need a continued stake in Hulu? Freer arrives after spending 20 years at Fox, where the Murdochs may be looking at Disney’s anti-Netflix move and wondering if they need to do more as well to combat the streaming giant’s efforts to effectively replace the MVPD ecosystem. The same might go for Comcast. If one or a couple of Hulu’s equity owners is looking to take on a larger role, it would make sense that Hopkins would look for an exit before the company is subsumed into a larger parent.

4. Change to Believe In. Hopkins came to Hulu in 2013 following a run as Fox Network Group’s distribution chief — and several years working for Vinciquerra. The Hulu move represented a big career step, putting Hopkins in the chief-executive role that he was never likely to reach at Fox where the Murdoch family rules and Peter Rice is firmly established atop the television group.

But Hopkins did not bring a deep digital background to a company whose culture is more Silicon Beach than Hollywood — where executives eschew offices in favor of an open floor plan and beer is available on tap in the office. Hopkins was believed to be well-liked and even-tempered, and his television distribution background was likely an asset as Hulu negotiated the carriage deals that made its live-TV bundles a reality. But with that product launched, its possible that Hopkins just wanted a return to a more traditional company with more traditional linear-TV problems.