I have an explanation for that, at least from a point of view that I support.
Putin and his cronies miscalculated before the war. They thought there wasn't a need to conquer anyone, to storm major cities and so on. What should have been done was just 'taking' these cities with clearance of some hotbeds of resistance afterwards.
When it became evident that a 'special military operation' format failed, two options arose - to carry on with somewhat limited war or escalate it with declaring a war and mobilization in Russia. And many people expected that the second option would be declared on 9 May during Putin's Victory Day speech.
But that didn't happen. Why? Maybe because Putin and his cronies feared a civil unrest because of that. One thing to cheer that in the front of TV, but another one to be drafted to fight in a war. Especially with possible troubles in the economy. Russia is projected to have a two-digit inflation and maybe a two-digit recession at the end of the year. Despite record revenues from energy exports in the first half of the year.
So, the decision was made to carry out the war in a 'special military operation' format with scaling down the goals. Now, it is a protection of the Donbas people. Denazification and demilitarization disappeared from public discourse.