The heat of competition? In order to meet a government deadline to launch humans from their new spaceport at Vostochny, the Russians had planned, though now cancelled, a single manned launch there in 2019, using a new rocket.
Their cancelled plans had included two prior test flights of the rocket with Progress freighters.
If cargo missions were successful, the one brave crew would ride into orbit from the new spaceport, knowing that in case of a serious problem with the rocket, the descent module of the spacecraft would parachute into deep forest of the Russian Far East or somewhere in the Pacific.
After “satisfying” this political goal with a single crew, all manned Soyuz and cargo Progress missions would then revert back to Baikonur for a safe ascent trajectory. The Soyuz spacecraft would continue flying two missions annually from Baikonur, until the veteran spacecraft’s final launch in 2025. In 2021, Soyuz spacecraft missions originating from Baikonur would switch from Soyuz-FG to Soyuz-2-1a rocket.
The Russians have now decided, rather than rush this first flight on the new rocket, to hold to the slower schedule.
This story is important to the United States. I think we must definitely end our dependence on the Russians before they make the switch to the new rocket. Based on the levels of poor quality control and corruption seen recently in Russia, I have grave doubts the new rocket will fly reliably at first. It would be a mistake to buy its use to put Americans in space.