leaver buster for an issue with riots game?

so i had noticed solo renekton only had been randomly crashing when playing league on stream and the same thing just happened to me and i got a leaver buster for 20 minutes, if someone can explain to me why its is randomly crashing, i have had no problems with the pc i am using now while playing league and it was my first game of the day and as soon as i walked to lane it just froze, i could move the league curser but i could not click on anything and heard no sound and it didnt even close the game i had to close it manually, any info on why this is happening would be amazing.