Buran was born dead, because it was so expensive, eats all money from programs it could launch.

Examples, Soviets planning space telescope like Hubble; martian sample return; long-duration heavy Venus rover.

Unfortunately, Soviet non-market economy was about 4-5 times smaller than US, so US have money for Shuttle payloads, but Soviets don't have.

BTW, Buran was by design much more expensive than Shuttle.

Because non-reusable parts of Shuttle where cheap SRB's and fuel tank, but expensive LOH-LOX engines saved. On each launch of Buran sacrificed equivalent to three Zenith rockets (essentially, Energia was unificated with Zenith, side boosters where very similar to Zenith 1st stage, and central block was Hydrogen, but costs similar).

The fun part about the polyus is due to something being mounted backwards, or software error, it did a backflip immediately after being released from its booster, thrusted retrograde and deorbited itself. It was supposed to burn prograde. Oops.

This was very probable for so brave new program.

- Energia, unlike most other Soviet rockets, only launch to suborbital trajectory (perigee under sea level), so payload have to add few hundreds m/s speed by its own engines to stay on more or less stable circular orbit, and have only few minutes to do this.

Development of Polyus was not careful enough, to make this operation reliable, because on all previous Soviet rockets top stage launched to payload target orbit.