Well, read this, if you want to understand the issues:
In the 1930s, Benjamin Whorf wrote a number of published and unpublished essays, proposing to identify phonetic elements within the writing system. Although some specifics of his decipherment claims were later shown to be incorrect, the central argument of his work, that Maya hieroglyphs were phonetic (or more specifically, syllabic), was later supported by the work of Yuri Knorozov, who played a major role in deciphering Maya writing. In 1952, Knorozov published the paper "Ancient Writing of Central America" arguing that the so-called "de Landa alphabet" contained in Bishop Diego de Landa's manuscript Relación de las Cosas de Yucatán was actually made of syllabic, rather than alphabetic symbols. He further improved his decipherment technique in his 1963 monograph "The Writing of the Maya Indians" and published translations of Maya manuscripts in his 1975 work "Maya Hieroglyphic Manuscripts". In the 1960s, progress revealed the dynastic records of Maya rulers. Since the early 1980s it has been demonstrated that most of the previously unknown symbols form a syllabary, and progress in reading the Maya writing has advanced rapidly since.
"1950s scholars found read Maya text of a breakthrough"
"In the 1950s scholars were able to read Maya text, in a breakthrough"
"Found" and "read" one after the other don't make sense, except if they were able to find somehow already read/deciphered Maya text, which based on Wiki was not the case: they deciphered it then first.
.... My specific question: One who has helped me and described the texts above failed to throw a light on the bold part. Is there anyone who could show me what really the bold part means?