Hillary Clinton was also a sore loser in 2016. She had sour grapes. No doubt about it.
However, between the "fake elector scheme" and the riot at the Capitol on January 6, 2021, it should be evident that Trump and his followers did far more than just claim that the election was unfair. They took active measures, and even resorted to violence, in order to overturn the outcome.
Finally, you are leaving out an important detail about Al Gore .... Even though he lost the 2000 Presidential Election by less than 600 votes from one state (where his opponent's brother happened to be the Governor), Al Gore not only never said that the election was rigged ... as the sitting Vice President, Gore also presided over the formal certification of his own defeat by calling the electoral votes into roll.
I can't imagine the frogs that would have rained down from Republicans in Congress if Gore had tried to contend that he had the Constitutional authority to not count the electoral votes from the state of Florida - as Trump tried to pressure Pence into doing in Georgia, Arizona, Wisconsin, Michigan and Pennsylvania.