Are you sure these games are just upsets or something foul is at play here because I have heard there are a lot of fixed games. Since I don't follow the esports scene this may sound like an urban legend but still can raise some eyebrows right?
Generally matches aren't fixed for CS:GO; some of the minor leagues might be fixed, but the big tournaments such as ESL or MLG are monitored and they will punish cheaters. It's the same with every sport really, there is always the possibility of teams throwing their matches.