Wikipedia has the story and the quoted text in a more readable format.

Nobody should be labelled "idiot" for giving a description of how the world looks. A physicist gathering experimental evidence for the theories of Albert Einstein does of course know the earth is not flat. I can imagine the portholes also contributing to this "2D-vision".

It's needed with a good and tight pressurized vessel to bring humans up to 50000 feet. The first pressurized flight cabins was created only ten years earlier.

50000 feet is not that high; modern commercial passenger airliners of today has 40000 feet as the maximum operating flight height (not because they can't fly higher, but because of security regulations - in case of a decompression event, fatalities can happen relatively fast if the plane stays at above 40 kft - for one thing, the standard emergency oxygen masks won't work well above 40 kft - even 100% oxygen it's not enough in such low pressures). Quite many ordinary flight passengers of today have probably seen the earth from almost comparable heights.

Rather non-scientific, but still interesting:

• They had to improvise to fix helium leaks on the way up (I wonder what the full balloon looked like, I can imagine the balloon itself should be rather difficult to access from the pressurized vessel.
• Despite the leak (that probably wasn't plugged very well) that they had problems descending (and almost ran out of oxygen)
• According to the photo on Wikipedia they made some really funny-looking helmets from straw baskets and textiles.
• If the photos are to be believed, scientists from that time of the history always wears formal clothes with a tie or a bow tie - I believe modern scientists going for such a mission would chose quite different clothing.