I've realized that I brutely lose or win by a mile when I get matched with usernames which have an Asian username and Asian clan name. I'm barely sure these are bots.
Since Clash Royal lets you play for hours on end, they need to make you stop playing because you could essentially climb all the way to the top in one sitting. Match making is done of card level and trophy level rather than tower level. So to make you force lose, they match you with an asian bot that counters every card you play.
Also, to retain players, they give you win streaks. These win streaks are usually super easy to win because all your cards are counters to the enemy's cards.
The only time I have fair matches are when I get matched with normal english usernames.
This is obviously only a theory, and just something I noticed.