That the real meaning of maths “was somehow unclear” was a truth about maths for about four-and-a-half millennia. Khufu built the great pyramid at Giza using simple maths, so this aspect —“the use of maths” — had been fully established from the beginning. It was the unavoidable “use of maths”. It gave maths a very positive, practical, public image. Then Plato came along 2,000 years later, and introduced a new vision of maths… as a form of superior language, a performance artform in effect.. Interesting discoveries had recently been made in geometry. Maths was a discipline which was widely admired. Many of the followers were attracted to maths because it was aristocratic … as well as a charming rule-abiding pursuit which offered an escape from the rough-and-tumble of the messy street milieu. This meant that the Platonists had no interest at all in where their maths challenges came from, or where they were destined to assist. More than two millennia passed, and it still has not dawned on the gurus of maths that their subject is a uniquely important confidence-builder.
Probably a secondary reason why this vision of maths never became the norm, was that there was another —more visible— explanation for maths’ celebrity. It was that the apparently aesthetic discoveries of the Platonic gurus occasionally sprang a surprise: sometimes they showed directly how complicated maths structures could be reduced to much simpler states… thus allowing initially stymied practical projects to be completed.
Some examples: ways were found to solve quadratic and cubic equations, difference methods were used to draw-up useful maths tables, e.g. sines and cosines. A few types of differential equations were solved. It was a fairly small “crop of results” considering the vast total investment of research hours involved …but as G. H. Hardy said in his book, it was these gems of “pure maths” which were “the most useful bits of maths”! (This “usefulness”, though, was relative to Hardy’s experience. He didn’t take into account the vast usefulness of maths as a confidence building discipline for people working on hugely ambitious projects.)
There also seems to have been a tendency towards the end of the 19th century for young mathematicians to dismiss Hardy-type challenges on principle. The public had been blinded by a succession of more and more abstract ideas, and were no longer able to understand what the mathematicians were up to. This was, with the advantage of hindsight, disastrous for maths’ good name: because it meant that young mathematicians could “do their own thing”, knowing that the public would not understand, to the slightest degree, what they were up to.
Eventually the Michelson-Morley experiment threw physics into crisis, because it appeared that the behaviour of light was relative to the observer. It looked-like —and was— a bottomless pit of incomprehension. This seems to have turned many of the maths gurus against letting mathematical physics call all the shots. There was no attraction involved in trying to solve problems of this extreme difficulty. (No one wanted to find that months had passed with not the slightest glimpse of a solution.)
Eventually the computer came along, and the Hardy-type of maths research virtually vanished. After 1960 it was automated maths which provided the confidence needed to pull-off ambitious projects. It was still a kind of “maths”, but the Barons of Silicon Valley called it “computing”, which they treated as chiefly accomplished by state-of-the-art- electronics. Maths had lost at a stroke its former applicable thunder.
Among the ranks of the maths gurus this was a loss which was hardly noticed, because they hadn’t taken any interest in applications anyway. In schools, though, this loss of applicability all the oomph out of the subject. So school maths has been paradigm-less for the last 50, years and it is failing to produce the number of enthusiastic polymathematicians we need —in a world which is now modelled at every level by maths.