I find it difficult to believe anyone in the entire world, much less the US, is misinformed enough to believe this. Quite a few of the cases did indeed allege fraud. Just one example:
" On Nov. 10, the Trump campaign filed a lawsuit seeking to halt the certification of Michigan's election results. It included affidavits from over 100 poll watchers who alleged witnessing instances of fraud... "
Many of the suits did not allege fraud, simply because they were addressing other matters, such as Pennsylvania's Democratic Secretary of State, who illegally extended the deadline for accepting mail-in ballots immediately before the election.
And of course we know inarguably there was fraud. In Georgia alone, for instance,
1,000 voters were found to have fraudulently voted twice-- and these were only caught because they were stupid enough to use their own name. Since the state doesn't allow ballots to be audited or signatures compared to the voter registration card, we'll never know how many people cast fraudulent ballots in a name other than their own.