He actually lost by about 22K votes. Between Wisconsin, Georgia and Arizona the total number of votes by all those states combined came out to Biden winning by about 45k. Interestingly enough Trump was ahead in all those states in the wee hours of the morning. By the next day Biden magically had won all those states and carried the election. If Trump wins those states its an electoral college tie. Now consider what happened in Nevada and especially Pennsylvania where Trump had a huge lead when everything got shut down for the night. Amazingly Biden had a lead the next morning all due to the enormous amount of so called mail in ballots that could not be counted until the next day for some reason and it is understandable why Trump felt the election was stolen. Not saying foul play came in to play here but it certainly was questionable enough to suggest something nefarious could have happened. If that happens to a Democratic candidate we would have never heard the end of it and all you so called election fraud deniers would still be up in arms. .
When someone makes a joke there's many possible responses. My go to, of late, has been to try and play along, depending on the joke of course.