Assuming this is true:

Tver [also known as Kalinin] was formerly the capital of a powerful medieval state. [...] it vied with Moscow for supremacy in Russia.

Power struggles in Russia going back centuries.

The high-speed train Sapsan, which connects Moscow with St. Petersburg, also makes stops in Tver, as well as the Tolstoy train connecting Moscow to Helsinki, Finland. [...] The newly designed high-speed railway line between Moscow and St Petersburg is expected to have a "New Tver'" station several kilometres southward of the city border.

Sounds like it was a quick escape route from Moscow, has a secret rail line to one of Putin's hidden fortresses, and has a quick escape out of the country if needed. There's also a military airfield for another escape route. I didn't see mention of any nearby army bases, which could be useful if the army revolts.