If their sincere belief is that the election was fraudulent, they would be trying to uphold the government, not overthrow it. Reverse the situation - Trump win

If their sincere belief is that the election was fraudulent, they would be trying to uphold the government, not overthrow it. Reverse the situation - Trump wins the election, but you believe that many of the votes cast for him were fraudulent. Would you consider yourself to be "overthrowing" the government by rooting out the fraud and putting in the person who you believe justly won? I'm not saying they are correct about there being fraud. I don't think they are. But the assumption is they the know the fraud is a lie and they are just deliberately lying to provide an excuse to illegitimately take over the government. I don't think that's necessarily the case. I think even Trump actually believes there was fraud to extent that he actually won.