I was researching another question and came across this article. It lists measurements of ash fall in various areas around the Mediterranean and in ice cores. I get the impression that most feel this evidence indicates a major eruption.
There’s literally no trace of a 2nd m BC Theran eruption in any ice core, anywhere.
The ash layer (actually undated, but assumed of course to be from the supposed supereruption) on Crete is measured in mm.
The caldera of Thera is 10s of 1000s of years old, perhaps 100s of 1000s.