I believe the theory of the big spoked wheels was two-fold: first, less likely to disappear in the spring muck of the steppes, and secondly, the open spokes were to allow blast energy from near misses to harmlessly disapate around the spokes. Kinda like the cage masts on American Battleships in that era.
Did anyone prove/disprove that energy disapation theory, either for the tank or the cage masts? Eventually, the US replaced the cage masts.
With the Tsar tank, the smaller diameter back wheels got stuck easily, and the engine apparently lacked the horsepower to drive forward when that happened. You'd probably need 3 or 4 large wheels to make the motive part of the tank work at all. It does look pretty outlandish today, but could you imagine some poor Austro-Hungarian peasant soldier watching 20 or 30 of these bad-boys advancing towards you across the prairie? Till you actually knocked a couple of them out of service, you'd probably soil your drawers first.
*edit* I don't think it had much for armor either, so our poor peasant soldier, if he sticks around, just might pepper it enough with machine gun fire where flakes of steel start spalling off inside the tanks crew compartment.