From speaking to Russians the overwhelming majority of people, especially in rural areas but also to a great extent in cities, probably correctly believe that elections are a waste of time because they’re not going to change the status quo or I guess if someone else is elected create a power struggle, so people just vote for the incumbent as they don’t want to cause trouble - the national attitude is “there’s nothing you can do about it”
While that’s very different from supporting Putin, it’s still intending to vote for him from a pollster’s point of view, so even in third party polls his “support” is going to appear higher than it is as they’re not measuring that, they’re measuring number of votes