Well when it comes to not '
starting conflicts', as you put it, then to that list of recent Presidents that didn't start conflicts you would have to add:
- Barack Obama
- Bill Clinton
- Ronald Reagan
- Jimmy Carter
- Gerald Ford
- Richard Nixon
- John F Kennedy
- Dwight D. Eisenhower
Non have officially brought the U.S. into a new war since 1945.
As to whether Putin would have still invaded if Trump had a 2nd term; I see it two ways.
There is a chance that Putin would not have invaded purely because Trump would have so weakened NATO, also probably tried to withdraw U.S. membership that NATO would no longer appear such a threat to Putin and that he wouldn't have felt the need to invade. That, added to Trump's love affair with Putin and attempts to get Russia back into the G7 etc. might have calmed Putin's probable paranoia with the anti-Russian sentiment from the West.
The other notion is that with NATO so weakened Putin would have felt even more emboldened and with even less chance of negative fall out or push back from NATO leaders and gone onto to finish the job he started back in 2014, with him at least annexing the whole Eastern part of Ukraine with it's majority ethnic Russian and Russian speaking population.
Thankfully as Trump, the wannabe autocrat himself, (you're no fan of democracy if you try to steal an election) didn't get a 2nd term we will never know.