But lack of competition doesn't mean no competition. You had several mining, automobile, shipbuilding, and energy company
Basically it means lack of competition. Central planing cause that goods from one factory are destined to some area and goods from other company to other area. Owner is the same (the state), so no reason to compete.
The only reason I see for Kremlin to favor one company is propaganda. Later they could invite western journalists and show them how great Soviet industry really is. But this is "very special" exception.
Automobile industry is a specific business. Communist countries were not leading in this industry. In Poland you had almost only Fiats and Polonezs, in Czecholslovakia Skodas and in Soviet Union probably Ladas. Polish state for example gave a license to Italian owners of Fiat to sell their inferior cars over here. Others were not allowed to the market.
About energy companies, just recently
in Poland they try to liberalize a bit this market. Before you have no choice at all, paid your bills to one supplier.
Soviets shipyards worked practically only for a goverment. No market here at all.
Communists sucks, checked many times...