Russians always liked big stuff. Their country is huge, lot of space, that might be one reason. They're known to produce 5 and 10 kopeks, among largest copper coins ever. Especially communism, industrialization and especially new rise of the Soviet Union after WWII let to project with excessive architecture, high scale urban planning, everything was big. Maybe they wanted to create a currency that impress you same moment when you take it in your hands. True question is why it wasn't released, like all of the 1958 coins. Probably as it wasn't practical. So, who cares...you've got smaller denominations.
Those '58 series seem to be ultimately rare, selling for thousands of dollars. I've seen only fakes that look like originals on photos. Would be very careful obtaining those.