You can kind of compare it to covid here. In 2020, the government told us we were going into lock down for the first time in all of our lives, we were living under a raging pandemic that none of us were safe from, we must go out only for essentials, not leave your local area or be arrested and do not visit older relatives, they could die. For the majority of us, we don't have any medical expertise to know whether this is true or not but the government told us as did the media outlets. Even medical professions I question how much they really no to be able to form an educated oposition. Iv worked in my field of employment for 10 years but if something new came out I couldn't claim to have much knowledge on it. As the pandemic has gone on, we have been told to take multiple vaccines, wear a mask, work from home etc. We have daily reports of death figures. A minority of people refuse the vaccine, they watch interviews where people denounce the virus, they post and read online articles supporting their views and they attend protests. Most people think they are nuts - and this has all happened and been accepted in 2 years.
Imagine growing up under Putin's regime. Your whole life could have been under his version of the truth. I would completely expect most Russians - particularly in Russia, to support the war. The ones attending the protests and speaking out are surely the equivalent of the covid anti vax brigade.