The new silver dragon made me quit DMing

Last night I ran a session for my usual group of 5th lvl players who are all new to D&D and are casual players. Only this time in the middle of the session, while exploring a town an Adult Silver Dragon appeared out of nowhere and with no warning attacked the party!!

Obviously as the DM, I knew it was my job to stop it from TPKing the party and the town so I tried to reason with the silver dragon but it did not listen :(

On the first round I asked the dragon to offer the party a quest in exchange for a truce but it instead used it's paralyzing breath on the whole party - they all failed the save. The next round I thought it would be a good idea to only target the paladin but the dragon wanted to use paralyzing breath on the cleric (as an intelligent creature i guess it knew the cleric is the only member of the party with support spells). On round 3 with most of the party already stunned or downed, as the DM I begged the dragon to stop its onslaught but it said that WOTC gave it paralyzing breath for a reason and finished killing the whole party. It then began paralyzing and rending the rest of the town until every single person was dead because "that is the optimal use of it's moveset".

My party are all mad at me for not controlling the dragon and ruining the campaign even though i explained to them that as a DM I tried my best but I am not at fault that a random Adult Silver Dragon appeared out of nowhere and killed all of them, I did after all ask multiple times for it to stop doing that.

Why would WOTC create such a monster when they are fully aware that it can just appear in the middle of a game and kill everyone!!!!

Is there anything I as the DM can do to prevent such an extremely powerful monster from TPKing my party in the future? Im afraid the possibility of this happening again will stop me from DMing for good!