From Destiny 2:

Destiny 2 experienced severe instability and server issues after a weekly reset, leading to players being unable to play or getting kicked out of activities. Bungie has confirmed that these issues were not related to a recent weapon bug but were the result of DDoS attacks from outside sources. Bungie rarely comments on such attacks, but decided to do so this time to clarify it was not due to the ongoing bug fix. Finding and taking action against the DDoSer may be challenging, but Bungie has a history of pursuing legal action against those who impact the game or its community. The game is currently functioning better, but it is uncertain if the attacks have completely stopped.

Read More: Full Article on Destiny 2

This kind of thing annoys me. Destiny is such a great game and has a huge player base and there is always someone who attempts to ruin it somehow for others. 

I am glad that Bungie came forward and were honest about this with their player base so that they know what is going on and know what to expect if it happens again.