If he lied on financial disclosures or other official documents for which a legal standard is established and is convicted of such, fine, remove him from office. However, the wheels of justice (if they even need to turn) won't act fast enough to justify not seating the Congressman-elect and making committee assignments like he's any other Freshman Congressman.
But, if his lies are confined to his resume and background which our adversarial press and his Democrat opponent failed to identify for voters before the election, where are we to find guidance for the hierarchy of lies dictating removal from or refusal to seat in public office?
Are some lies worse than others? Are campaign promises summarily forgotten once they assume office grounds to have Congressman removed? Are their oaths to support and defend the Constitution compromised when Democrats contribute to bail out unquestioned rioters and looters as our VP and others did? How about President Biden's refusal to enforce our laws protecting the country's sovereignty? Who will take responsibility for scrubbing the resumes and claimed backgrounds of current Congress Critters to ensure none of them lied as much (or more) than Santos?
Are lies on their resume or about their background BEFORE being elected worse then telling lies as a sitting Congressman about the supposed existence of "evidence" proving the duly-elected President of the United States had supposedly conspired with the Russian to get elected and remained an agent of Russia after assuming office? If they aren't (and I don't think they are), one cannot without major hypocrisy support the investigation of, removal of, or refusal to seat Congressman-elect Santos without also calling for the removal of at the least Adam Schiff. His lies about the Russian Collusion Delusion are not in question.
When it comes to our elected representatives and lies not addressed by a legal standard, acting on those lies is a slippery slope we ought not to go down no matter which team you support. Our only recourse should be advocating for and contributing to the campaign of their opponent in the next election.