Was it possible at all to understand the article? Even if you stated that article was unclear, saying that XYZ failed to get it, in spoken language, implies failure, implies that there was an alternative.
Purely logically it does not imply it, and to assume otherwise would be fallacy. But we are not looking at every statement as pure logical arguments.
To make things less biased you can try several approaches
1) connect the two sentences
The article was unclear and therefore XYZ could not understand the idea that it tries to convey.
2) turn it into passive
The article could not be understood by XYZ.
which is quite neutral in assigning the blame. Joining the two statements makes puts more blame on the article:
Since the article was not clear it could not be understood by XYZ.
3) don't present XYZ as special case
The article was not clear and many had problems understanding it.
if you must mention XYZ, mention them after the above statement is also less biased
The article was not clear and many had problems understanding it. For example XYZ.