I agree with you Glen in the sense that given the Republican trifecta at the moment they would rather see him resign then have to go through the impeachment process.
First the impeachment would have to pass though the House, then a long drawn out trial would be held in the Senate with Justice Roberts presiding.
It may not matter, I believe Dear Leader is looking for a way to declare victory and resign right now. For instance if he were resign before Sept. 30th he would incorrectly make the claim that he had the record unemployment(lie), brought millions of jobs(lie), and passed more legislation in the first 90 days than any other POTUS(lie).
In exchange for his resignation he would ask that all charges stemming from Mueller be dropped. Although at this point I'm not sure Mueller would drop the charges.
Of course the second he left office he would be slammed by NYAG with no less than 4 grand juries. Money laundering, Fraud, RICO, & Human Trafficking.