ARK Invest's Cathie Wood is curling up on the couch to binge invest in Netflix (NFLX -0.51%) this week. She's also lightening up on her stake in fellow streaming wunderkind Roku (ROKU 1.91%).

For many investors, Netflix and Roku seem to be joined at the hip in the streaming video revolution. Netflix is the top dog among premium services with 207.6 million paying subscribers by the end of March. Roku is the streaming gateway of choice for 53.6 million homes across the country.

Why did Wood buy shares of Netflix on Tuesday? Why did she also sell shares of Roku on Tuesday? We don't have official responses. ARK Invest's transparency ends at its daily transaction reports. However, let's try to make sense of the two seemingly contradictory moves.  

Someone channel surfing while curled up on a couch.

Image source: Getty Images.

Channel surfing 

It's important to remember that Netflix and Roku aren't necessarily passing ships in Wood's eyes. She routinely trims and adds to some of her largest positions. Just a couple of weeks ago we were wondering why she was selling shares of Netflix, as she had lightened her position in the streaming service pioneer four times over the five previous weeks. The stocks that she's selling today Wood may be buying right back tomorrow. ARK Invest made four different purchases of Roku through the first half of May, even if Tuesday's transaction is the third time that she has sold shares of the fast-growing streaming hub since its springtime shopping spree. 

Roku investors don't have to start getting nervous here. ARK Invest still owns more than $1.5 billion worth of Roku stock, making it the second largest holding across all of its funds. 

It's hard to argue with Wood's success after the monster run that the ARK Invest ETFs had in 2020. If you're a Roku investor you can hope that she's simply pruning back her Roku position to raise capital to buy some recent IPOs that she's been eyeing lately. 

Netflix and Roku will be just fine. They have both secured what I like to call invisible moats. Netflix competes with streaming services put out by giant media stocks, but as the runaway revenue leader no one can invest as much in new content as Netflix can out of its cash flow. Roku also competes against some heavyweights. Three of the country's four most valuable companies by market cap operate rival streaming hubs. Roku's independence -- as well as its agnosticism and first-mover status -- have helped it prevail as the operating system of choice for smart TV manufacturers. 

It's OK to cheer that ARK Invest is buying back into Netflix again after seemingly easing up on the cable and TV industry disruptor last month. This doesn't mean that you have to read too much into some light trimming of Roku. The two companies rocked during the pandemic when consumers had to hunker down in their homes, but they're stronger now even with folks heading out again. They packed years of growth into a handful of quarters, but that finds them with much larger audiences to serve right now. The success of Wood's ETFs continues to be tied to positive outcomes at both Netflix and Roku.