Bayern wanted to repeat the formula that landed them Philippe Coutinho a few years ago. They paid a loan fee for a year and agreed to pay his wages, and then had an option to buy him outright. Bayern chose not to exercise that option, and Coutinho returned to Barcelona. He was eventually sold to another team - Aston Villa.
De Jong has had two proposals on the table for some time now - Manchester United and Chelsea. He has so far refused to agree a move to either club despite Barcelona hoping to sell him if he does not reduce his salary.
Bayern do have his friend and former Ajax teammate Matthijs de Ligt in the squad, plus they are considered one of the favorites to win the UEFA Champions League. There was hope within the Bavarian club that that would convince De Jong to leave the Camp Nou.
United in particular are said to still be insisting in his signing after getting Casemiro from Real Madrid and winning 2-1 against Liverpool. His former coach at Ajax, Erik ten Hag, who now coaches United, is said to be a great admirer.
A loan would’ve allowed Barcelona to continue looking to buy Bernardo Silva from Manchester City. However, this offer runs into a similar problem that the Coutinho deal ran into - what if Bayern decide not to use their purchase option? It seems that, for that reason, Barcelona have discarded the request. That means De Jong remains likely to stay.