Because various members of the Republican fringe have told them that the Ukrainian government is in cahoots with Biden and the Dems so, with the dog-whistle 'owning the libs' and on the basis that 'my enemy's enemy must be my friend', they fall in behind Russia. Thus completely blinding themselves to the shit that Putin is doing, ignoring any evidence to the contrary as 'the MSM telling us lies' in the same way that they won't belive anything bad about Trump despite all the evidence out there.
It's so polarised over there - politics is broken in the US. It's not that brilliant here either but thankfully not as bad as there.