https://bandaancha.eu/articulos/justicia-ordena-operadoras-b...
It's in Spanish, but the relevant part translated:
The investigating judge, Santiago Pedraz, would have requested information from the company that manages Telegram, without having received a response, which is why he has chosen to order the telecommunications operators to block access to the servers that maintain the service, according to Europa Press1. . El País adds2 that Telegram would have refused to provide the requested information, probably related to the identity of the group participants.
The company that is in charge of Telegram messaging has been domiciled in the United Arab Emirates since 2017, although its parent company, Telegram Group Inc, is located in the United Kingdom.
At the moment Telegram remains operational in Spain, but the order is expected to come into effect in the next few hours, which will force large operators to block access to the IP addresses of the servers.
Pre-emptively blocking the entire app "while claims are investigated" seems pretty extreme. I thought that sort of thing was only done if 1) the judge thought the petitioners would almost certainly win, and 2) there would be irreparable harm done otherwise. Hard to see how #2 could be the case for copyright violations.