Well, the short answer is that they likely did not learn 'hoplite warfare' at all. The modern opinion on whether 'hoplite warfare' ever really existed in Greece, at any time, is contentious, but it seems like the trend is to deny its existence almost altogether. There is a possibility that something of the traditional vision of 'hoplite warfare' did exist, though if it did it was only for a short period of time. In this light, the question of whether or not the Etruscans ever practiced 'hoplite warfare' is moot, but I will elaborate.

Arms and armour which have been identified as 'hoplite' can be found in Etruscan contexts dating to the seventh century BC (perhaps earlier); these include round shields which look like aspides, spears depicted similarly to how Greeks depicted them, and Corinthian-esque helmets. But, this is alongside depictions of horsemen (very common), archers, warriors/soldiers with axes, etc... There was never a complete 'transition' to 'hoplites' in Etruscan iconography. Save the bizarre opinions of Adam Schwartz, the appearance of the aspis does not mandate 'hoplite warfare', so there really is no need to jump to any assumption based thereupon.

The general picture of warfare that we get from what sources we have, is one of raiding, sieges, battles, and naval warfare. A broad mix, also present in Hellenic warfare, but counter-intuitive to 'hoplite warfare'. A number of authors have postulated that the social structure of Etruscan city-states would not have supported 'hoplite armies' (i.e. D'Agostino).

Even if you believe in the hoplite 'orthodoxy', it is unclear how the Etruscans would have learned 'hoplite warfre'. There is no reason to assume that the Western Greeks practiced this type of warfare, which is typically how the adoption of 'hoplite warfare' in Central Italy came about (see Snodgrass' essay in the 'Peer Polity Interaction' volume).

The adoption of arms and armour that look like Greek examples was likely an element of fashion in an Etruria that was forever interested in display and prestige. There is archaeological evidence for 'foreign' influence in Central Italian arms since the Final Bronze Age, this time coming from the Atlantic coasts of modern-day Spain and France. In the Early Iron Age, there was considerable influence from the cultures of Central Europe (Slovenia, Romania, etc...) in the form of helmets. During the same period there were also connections to Northern Europe, although these are a bit unclear, some antenna swords (mostly found around Tarquinia) were clearly influenced by, or influence to, sword types found in modern Germany, Scandinavia, and Poland. In the period immediately before the coming of 'hoplite arms' to Etruria, the Near East was the source of considerable influence. I think it far more likely that Etruscan elites liked to keep up with wider Mediterranean and European fashions, as a means of display, than continually changing their practice of warfare.

There are some good papers on the Early Iron Age to be found on the academia.edu page belonging to Cristiano Iaia (in English). For the 'hoplite' period you will have to resort to the books by Saulnier and Stary (French and German, respectively), or to Stary's article in English (https://www.cambridge.org/core/journals/proceedings-of-the-prehistoric-society/article/foreign-elements-in-etruscan-arms-and-armour-8th-to-3rd-centuries-bc1/15F128ABD465076A516C541BD17C44D0) thought these are all outdated now. Unfortunately, my book on the topic will not be out for a few years, so you will have to wait until then for a modern discussion of the evidence.