I've read in a number of places that around the time of the Persian Wars through to the rise of Macedon bronze and even linothorax(thoraces?) panoplies were discarded even by the wealthier Greek citizen soldiers in favor of a less cumbersome hoplon of a helmet, spear and aspis shield. How much truth is there to this? I've heard varying accounts, some, such as Donald Kagan, love to relish in how much better equipped Greek infantry was compared to the multi-ethnic invading Persians in lighter gear; according to him, this was key to their success in resisting them. If this was true, why would they ever give it up? To what extent did they actually give it up? What evidence do we have that attests to it? For example, would Xenophon's '10,000' mercenaries have been mostly bear-chested? How many of them can we guesstimate wore breastplates, or at least some form of thorax? We know they gave up some of their gear to lighten their load and fight ekdromoi style, does this suggest that many had opted to go full panoply in the first place?
I know about the development of 'ekdromoi' hoplites, who 'ekdrome' and can better adapt to situations outside the phalanx, I understand some of the reasoning... But can I get a detailed account as to what developments took place that would cause such a shift towards objectively inferior defense in favor of more maneuverability-- and to what extent this was true? It's all a bit confusing; how sweeping was this change, and when did it start to reverse? Pezhetairoi seem to often be depicted with linothoraxes, but is this accurate? I've often heard it said that the sarissa was actually the main form of defense for the Macedonian phalanx... Philip obviously would have been savvy to the latest trends in Greek war-fare, having grown up under Epaminondas and Pelopidas (excuse the pun), right? Did this situation continue into the Hellenistic period? Is too much perhaps made of this? Would wealthy eupatridae opt to march into battle bear-chested, even if they could afford a fabulous bronze bod, or a scaled linothorax? How major of a change was it, and what evidence do we have that armor was or was not important in this (admittedly rather long) period. It just seems like there are conflicting opinions, when you hear the popular 'Greeks reinvented heavy-infantry with the phalanx and their armor really helped them beat back the Persians' espoused by certain people, and then you also hear people frequently say 'most Greeks chose not to wear body armor in the classical period even if they could afford it'. How sure are we of any of this?
Bonus question: Was the linothorax linen or leather based? It seems like people are divided on whether it was linen or leather and I've heard convincing arguments both ways. If it was indeed linen, how much evidence do we have that leather was used for armor in the ancient mediterranean (again, have heard conflicting argumetns)?
There are tons of questions here, but I answered most of them in this older thread. The basic points are these. The notion of the lightening of the panoply is based on fairly consistent iconographic evidence showing ever more lightly equipped hoplites, on the dramatic drop-off in dedications of armour from circa 500 BC, and the implications of various literary passages. It is not based on any explicit statement or discussion of armour, since no such discussion survives. This means we will never be certain of the answer to most of the questions you're asking. Much of it is disputed because different interpretations exist. The literature can often be read in multiple ways, dedications may disappear because of changes in religious practice, and the problem with all vase paintings and reliefs is that we cannot tell the difference between idealising and realistic depictions. We do not have the slightest ancient evidence as to why hoplites seem to have become less heavily armoured (if that is indeed what happened), so all accounts of the change are speculative.
The most persuasive argument in my view (but there are many others) is that individual warriors may choose to reduce their own load if they believe they are protected by others. Just as the heaviest panoply coincides with an age of "heroic" forward skirmishing of individual rich men, so the lighter panoply emerges in a time when hoplite bodies become more organised and mixed forces are increasingly effectively used for mutual protection. It also coincides, though, with the democratisation of hoplite service, in which more and more people could afford the basic gear of the hoplite but not necessarily the full bronze kit. This also means that richer hoplites may have continued to wear heavier armour, blending into a crowd of more lightly equipped fellow citizens, though in the Classical period the richest men mostly switched to serving as cavalry in order to distinguish themselves from the common people.
This should be separated from the question whether Greeks had an advantage in body armour during the Persian Wars. There are several examinations of this question in recent scholarship, all of which conclude firstly that most Greeks would not have worn the full kit (contrary to the belief of people like Kagan), and secondly that many Persians would have worn body armour of their own. The difference between the two sides on this point therefore largely disappears. Herodotos’ claim that the Greeks had the advantage due to superior armour must rest on the fact that all Greek hoplites would have carried the large wooden aspis shield, whereas the Persian infantry mostly carried wicker shields, smaller wooden shields, or no shields at all. But in any case, the Persian army contained heavy infantry from numerous subject peoples, from the Egyptians to the Assyrians as well as many Greeks; they certainly wouldn’t have been surprised by Greek hoplites, and in fact their armies had regularly defeated Greek hoplites until that point.
The ekdromoi don’t really have anything to do with the matter either. There is a weird tendency I've noticed among some reenactors and pop historians to present the ekdromoi as some kind of deliberately formed and prepared unit. This is completely false. These troops never existed as a distinct unit and were never intentionally developed by any army. The ekdromoi were nothing more than ad-hoc groups of men formed in a few emergencies because they were younger or (less commonly) more lightly equipped than the others. These men were not ekdromoi until the order was passed down; since the age classes called up to charge out would vary, few would ever have expected or prepared to serve as ekdromoi, and this was never more than a stopgap measure. Hoplite columns were supposed to be protected by light-armed troops and cavalry; ekdromoi were only ever needed because a commander had failed to prepare adequately and had no other recourse. They were usually unsuccessful in their role.
The linothorax is obviously, by definition, made of linen. The word literally means "linen body armour," and its construction out of linen is discussed by Herodotos. The question that people debate endlessly is not whether the linothorax is made of linen, but whether "linothorax" is indeed the name Greeks would have used to describe the so-called Type IV or "tube-and-yoke" cuirass seen in art. The two are never explicitly seen together, which leaves some people free to argue that the linothorax is entirely separate from the tube-and-yoke, and, much more tenuously, that the proper term for that cuirass is “spolas” – a word twice used by Xenophon (and nowhere else), which much later lexicographers claimed was a form of leather armour. On these extremely thin grounds, it is often argued that the tube-and-yoke armour may well have been made of leather, even though leather armour is otherwise unknown to the Greeks until the later Hellenistic period and generally very rare throughout history.