According to him, the USSR military developed Buran to match what they saw as the space warfare capabilities that USA gained with the Shuttle. Unlike the ICBMs, the shuttles decoupled the event of the payload launch from event of the payload delivery, i.e. bombing. The early shuttle missions demonstrated the ability to "dive" to an orbit from which they could deliver a nuke directly to Red Square and then return back to the low Earth orbit. Shuttles could also perform attack missions against targets in the Earth's orbit, approaching and destroying USSR's satellites as a prelude to a nuclear war.
Buran was designed to perform both of these missions. Unlike the shuttles, Buran could perform them while 100% unmanned. Until this X-37B flight, US did not have a public demonstration of a technology matching what USSR had with Buran in the late 1980s. Given the "hot peace" nature of the contemporary relationship between US and Russia, it is not surprising that US would want to demonstrate that it went above and beyond what USSR accomplished in space warfare. X-37B does that.
If you are wondering about the 2-year mission for X-37B: when Buran launched in 1980s US immediately started speculating that the "unmanned" capability of Buran was just another lie by USSR. Can't say the same about about X-37B considering that it was in orbit for twice the time of the longest manned mission.