Why we needed Kayexalate in the first place

In February I'm giving grand rounds on the Potassium Wars (what, you didn't realize we are in the opening stages of the potassium wars?). I was looking at the original research on Kayexalate from 1961 and came across this ad. Check out the doses of spironolactone they were slinging:

400 mg of spironolactone, daily and this is in a world without loop diuretics!