Moscow Theatre was an Inside Job by Putin's Spetnaz (Special Forces). Putin does these kind of events to emanate fear among the Russian people to gain more control. Here are a few other Inside Jobs by Putin to gain popularity to attain Presidency.

https://en.wikipedia.org/wiki/1999_Russian_apartment_bombings

https://en.wikipedia.org/wiki/Moscow_theater_hostage_crisis

https://en.wikipedia.org/wiki/Beslan_school_siege