This explains your question, I guess.
How many individual investors have the resources to do this kind of work? And he is Buffett, and while he was young at that time, he had some experience of thinking and acting like a businessman. Buffett himself said along the lines that people think that they cannot become like Bill Gates but they can become like Buffett.
One can get inspired by anything, expand horizons by looking at different things, but we have to consider other things too.
Polycab is not in the same line of business as American Express, but is Polycab as popular a name now as American Express was that time? Was American Express a monopoly at that time or was it a duopoly or oligopoly, and what is Polycab in this regard? What valuation was American Express trading at, and what was its valuation when it fell 41%? Buffett AFAIK was a value investor in those days, so he must have looked at the opportunity from valuation perspective too, and as he is Bufffett he buys stakes, not just shares. What is the current situation of Polycab w.r.t valuation? It is trading at ATH.
Investors who have been the following a business for some time may not think twice in situations like these, but if taking a new position, one must consider other things too.
Just saying, as I too from time to time find things like this, certain stocks appearing as value, particularly when they are discarded, and I do know that these could be opportunities, but the fall is just 5.4% from the top.
If you are interested, you can read Prof. Bakshi’s posts in this thread, to have some additional insights.
No position in Polycab.