While royalty had a big impact on what the elite wore, the style was also influenced by tailors and tailors guilds. The type of clothing that became popular with royalty and the nobility also depended on the availability of fabrics and dyes. So fabric merchants also influenced style when new trade routes opened and beautiful new materials were imported.
The Church had a huge influence on what people wore in the Middle Ages as did the government, both who established rules on who could wear what and when they could wear it. Traditional values demanded that people wore head coverings in public, dressed modestly according to their station. What you wore depended on status, class, gender, and occupation.
The rise of the individual designer did not come until centuries later.