As per the article:

Before anything could be done to potentially decrease Superfest’s extreme durability, the brand’s parent company, VEB Sachsenglas Schwepnitz, went bankrupt after the fall of the Berlin Wall in 1989.

and Wikipedia:

With the political change, the GDR glass industry and its scientific institutions began to be wound down.

this would appear to be a result of East Germany being annexed into the capitalist West Germany, which happened 9 November 1989 – 3 October 1990.

Without commenting on East Germany, the annexation was handled terribly, and it’s the reason AFD is rising in popularity in eastern Germany these days.