Too many events and so-called fact checking here. In simple terms, Trump was the only one to allow the shipment of weapons (importantly Javelin missiles) to the Ukraine, before Putin invaded.
Obama stuck to his refusal to provide weapons or other lethal military gear to Ukraine.
https://www.congress.gov/116/meeting/house/110331/documents/HMKP-116-JU00-20191211-SD994.pdf