in the old language of international law - and putin is an old timey conservative, like a disraeli or a churchill, although this is even older than that - dignitaries need to meet at the proper levels. this is actually why the american presidents, before trump. wouldn't meet with putin. they were spitting this back in his face.
emperors meet emperors
kings meet kings.
governors meet governors.
mayors meet mayors.
diplomats meet diplomats.
putin, as an emperor, demanded to meet with an equivalent dignitary in the west, namely the president of the united states. obama and biden both responded by refusing to meet with putin, in an attempt to enforce the idea that russia and the united states are not at equivalent levels, that russia is a subservient state and america is the hegemon. putin could meet with john kerry, or anthony blinken. the russians rejected this as inappropriate.
putin, as emperor, could not possibly meet with zelensky, who is at best a governor and perhaps merely a mayor. zelensky would need to meet with an undersecretary below lavrov. that would properly enforce zelensky's status.
zelensky, by demanding to meet with putin, is essentially being uppity.
the russians won't tolerate that. zelensky must meet with his equals, at a lower level of function, as is the convention in the lost world of hierarchy that the russians continue to exist in, and which the rest of the world barely remembers or understands.
there was no possibility of this ever happening, and trump's insistence on it was either ignorance or dishonesty.