Complex sentence: Having never become official or popular, Glinka's anthem was soon replaced under Yeltsin's successor, Vladimir Putin, who preferred the old Soviet anthem, which was approved by the legislature in December 2000, with Putin's signature and modified lyrics.
Split into simpler sentences: Having never become popular enough, however, Glinka's anthem was replaced soon after Yeltsin's successor, Vladimir Putin, took over. Putin preferred the old Soviet anthem, which was approved by the legislature in December 2000, with Putin's signature and modified lyrics.