Nothing got in the way .. The wheel was invented a long time ago, as well as its dimensions. Besides, the first bicycle (scooter, balance bike) had the same wheels .. It depended on the conditions and traditions. Your question sounds strange, for example, why does a cart have two huge wheels, and a cart has four small ones .. and a Roman chariot has two ??? What was in the way ??
Large wheel - great stability with rotating wheels. In addition, the drive was from the front wheel. However, more efforts had to be made. To put less effort, a chain drive with a drive to the rear wheel was invented. It is much more convenient to pedal and less effort. When the pedals were in the middle of the bike, it was advisable to make the wheels the same. A compromise is always sought for stability, speed, effort expended.
The larger diameter of the front wheel allowed the bike to reach high speed. Because the pedals were attached to the wheels directly, without gears and chains.
Firstly, then there were no asphalt and other smooth roads. Secondly, chambers with air in the tires were invented later. The maximum that was then was cobblestone pavements, and now you try to drive straight on the pavement on small wheels without wobbling and, moreover, will not fall over and crush someone.
In the very first models, they were just plus or minus the same.
Penny-farthing model, in which the front wheel was much more than the rear one associated with the pursuit of speed data - in one pedal rotation, a large wheel made a whole circle and covered a huge distance. This model, like all the previous ones, had pedals connected directly to the wheel, which caused these difficulties.
These bicycles, by the way, did not last so long - a couple of decades. But their appearance is so strange that they have become one of the symbols of the era, and in various cultural things like cinema, they are perhaps even more common than it was in reality.
With the advent of chain transmission, the rules have changed - it became possible to increase the number of revolutions wheels relative to the pedal speed without increasing the diameter of the wheel itself. Well, and, accordingly, since then large wheels have sunk into oblivion, giving way to more comfortable and safer low, regular bicycles, which for more than a century have retained almost the same design as the first bicycle with a chain drive.
If we look at the history of bicycles, we will see that the so-called penny farthing (they got this name because one wheel was large and the other small, like two different English coins) were popular for a short time and were rather a product of fashion than engineering designs. Therefore, as soon as the so-called safe bike appeared (even its name indicates that penny farthing even in the past was considered not very safe for people), it quickly replaced the old design.
Just because of their unusualness, they often appear in the works of mass culture, as such a symbol of the past, so if directors shoot a TV series or film about the 19th century, they would rather put the heroes on a penny-farthing, so we get the impression that in the past everyone rode exclusively on such bicycles.