what makes the most sense to me ( and this is just my perception, take it with a grain or even two grains of salt ) wrt the titans reacting to the elves crafting bodies, is that it came out of the spirit-born overreaching / taking more than what they put back, upending the beyond's interconnectedness. we don't get any kind of lore on how spirits and titans coexisted beforehand, and for the elves' side of things, we have a very unreliable narrator - two, if you count mythal. spirits and elements and what have you operate of their own accord, but they were all pillars of what the beyond used to be. all of them were touched by it. all of them benefitted from it. all of them fed into it. borrowing far too much and affecting another living thing's connection to the world/beyond would be a rightful cause for reaction, whether they realized what they were doing or not. the blame lies therein when they didn't attempt to mend their mistakes, and instead just ripped the titans away from that connection altogether. like what bishop said: the evanuris doubled down, and the titans responded proportionately.