This is the explanation given by Twitch. This modification would have left open the possibility of unauthorized access by third parties, with the consequences that we know.
The editor also wishes to reassure: passwords do not have been exposed, nor the banking information, including the means of payment.
It confirms that the data taken contained documents from the deposit of the source code and part of the accounting information of the broadcasters, in other words how much money these people make on Twitch.
The latter ensures that this information only reaches a small part of its users, that the persons concerned are contacted and that the impact on customers is minimal. The publisher of course reiterates all the seriousness it takes in its responsibility for data protection, measures having been taken to strengthen security.