Gear damage

Good day. I’ve been driving Volvo since 2009 and I’ve already leased some models, including V70 and XC60. I’m currently driving my second XC90, it’s a B5 diesel. I’m very happy with the car so far, would say it’s my best Volvo ever. I’m driving about 22,000 km a year, of which 75% long distance. My Volvo has run around 90,000 km. A few weeks ago I heard a kind of howling or buzzing at the time of giving gas. The Volvo has been in the workshop since the beginning of the week, and now it says that the transmission is over. It has to be replaced and because the spare parts situation is difficult at the moment, it can all take a good three weeks. Blöd, I wanted to ride with the car on vacation tomorrow. The Volvo statements irritate me. Therefore, my questions here in this forum: Is this normal that the gearbox in a mature premium vehicle like the XC90 is broken after only 90,000 km? Does it deal with a known problem and is therefore perhaps a case for the culanz? What do you need to repair?