The official news announced by the ISRO chairman on the live broadcast was "the last signal received from the lander was 2.1 KM from the lunar surface. Data is being analyzed as of now".
In all probability indicates a crash landing.
In all probability indicates a crash landing.
Although the something going wrong could be as innocuous as losing antenna alignment, which happens often during landings even when nothing is really wrong, because the spacecraft is changing pitch to effect the landing.
So my best guess would be loss of telemetry due to loss of antenna alignment, followed by a bad trajectory for some reason, followed by unintentional lithobraking.
Per Twitter, it seems like something went wrong during the braking burn. The spacecraft was left tumbling (which certainly wouldn't help antenna alignment), and was thus unable to effect its landing burn.
No idea yet exactly what caused the tumbling; there's a variety of potential causes.