IMO social media and the widespread dissemination of misinformation have fueled the rise of conspiracy theories. What I find interesting is how this skepticism has shifted over time. Remember back in the 80s & 90s, it was largely liberal Democrats (particularly those in the naturalist and holistic health movements) who were distrustful of vaccines, pharmaceuticals, and anything not deemed "natural." Concerns about autism, preservatives, and Big Pharma’s influence were primarily associated with left-leaning advocacy groups.
Fast forward to today, and it’s the far-right conspiracy theorists leading the way against vaxs.. The skepticism has morphed from concerns about toxins and "natural immunity" to fears of government control, deep-state agendas, and even population manipulation.
Back in the late 90s opposition to vaccines was significantly influenced by people like RFK Jr and groups focused on organic living (most leaned left). If you reacall, The 2015 Disneyland measles outbreak was mostly tied to wealthy, liberal areas where a lot of people were skeptical about vaccines. Then comes the COVID-19 pandemic and the big ole shift...vaccine skepticism shifted over to right-wing groups, fueled by social media echo chambers and distrust in government mandates. There's your change.