It really is very easy to understand – Bérenger Saunière got over 200,000 francs from trafficking in masses between 1896-1915 and the evidence exists in Saunière’s own handwriting (below). This explains his activities and consigns all the “mysteries” and “treasures” into the trashcan.

It really is not that difficult to understand.
It’s straightforward.

“At the end of the last century he had a rather original idea. He placed in foreign newspapers, especially in the United States, an advertisement announcing that the poor priest of Rennes-le-Château lived among heretics and had only the most meagre of resources. He moved the Christians of the whole world to such pity by announcing that the old church, an architectural gem, was heading for unavoidable destruction if urgent restoration work was not undertaken as soon as possible.

“The priest received considerable sums, so considerable indeed that one fine day a whole team of masons and workmen was to be seen arriving in the village. But instead of stopping the worthy old church from falling down they started building a villa in Rococo style flanked by an immense keep, from where one can survey one of the most beautiful landscapes in the entire region. And the gallant priest continued feasting and merrymaking in his new home” (Roger Crouquet, Le Soir illustré , Number 819, pages 16-22, 1948).

There is no reason to introduce convoluted arguments over a simple fact.