Roundhill Investments' Dave Mazza says the "fundamental footing" for markets remains strong, though recent weeks have shown "more fragile" movement. He believes the A.I. shakeup is the leading culprit behind the fragility and makes the point that 2026 will be the year of "winners and losers." Dave notes Alphabet's (GOOGL) outperformance and rising competition against Nvidia (NVDA) as an example. As for sectors he expects to shine, Dave tells investors to watch healthcare.