As u/itsallfolklore explains here, mediaeval people believed dragons to have existed in the past and to still exist in distant lands. So they did not fear dragon attacks, any more than they feared for instance lion attacks

Hi, you may look at the answers on this previous post : https://www.reddit.com/r/AskHistorians/comments/qm6b5p/when_did_christians_stop_believing_dragons_were/

I adressed this issue in my own answer to the question. Here it is copy pasted:

Hi,

I may provide some elements of answer to your question which is in fact rather complicate to answer as it involves different field of history: story about dragons are found in different timeperiod and different geographical area in the christian world.

One key aspect of your question is the notion of "believing in dragon". To be clear, medieval people did not believe in dragons in the sense we may expect. The conception of dragons of medieval European christian was different from what we may observe in modern works of fantasy.

I will speak of the area I know the best, medieval Scandinavia, but some of these info may be valid to some extent outside this context. In Old Norse one of the most common name for a creature which we would translate by "dragon" is ormr, meaning worm, snake, serpent and which while having some of the characteristics of our "dragon" has generally neither legs nor arms or wings. In fact this conception of dragon as a big powerful snake is also found outside Scandinavia. The dragon which Yvain fight in Yvain, le chevalier au lion by Chrétien de Troyes is called a serpent that is a snake in french. Medieval people had no conception of phylogenetics categorization of living beings. To them animals were not classified according to their degree of proximity as species but on other criteria, one of which may be the appearance of the animal. (To some extent we still do that in the common language when we speak of "fish" as a category while fishes are not a real biological category). In this sense, to them, a worm, a serpent and a dragon may very well fit in the same category, that of long being crawling on the ground. On the other hand, Old Norse also have the word "dreki" cognate with our "dragon" and which seems to be more often found in relation with winged dragons. The notion of dreki may have been a borrowing from the european depiction of dragon as winged creature. It shows that Old Norse speaker made, at least sometime, a distinction between very big snakes with human intelligence, and winged lizards. In anyway it must be clear that the distinction between some animals which we deem as real, such as snakes, and some creatures which we consider mythical, such as dragon, was not that clear in the middle ages.

As such dragons, and some other mythical creatures, were less perceived as species of their own than monstruous and abnormal versions of known species. But medieval people did not expect to see these abnormal beings in their neighborhood. In the medieval christian worldview the abnormal and monstrous was especially seen as belonging in the remote uncivilized parts of the world or in the distant past, either pagan past or the legendary past of chivalric golden era. A famous passage of Chaucer describes how the world became less "magic" after christianization:

In th’olde dayes of the kyng Arthour,

Of which that Britons speken greet honour,

Al was this land fulfild of fayereye.

The elf-queene, with hir joly campaignye,

Daunced ful ofte in many grene mede.

This was the olde opinion, as I rede;

I speke of manye hundred yeres ago.

But now kan no man se none elves mo,

For now the grete charitee and prayers

Of lymytours and othere hooly freres,

That serchen lond and every streem,

As thikke as motes in the sonne-beem,

Blessyngue halles, chambres, kichenes, boures,

Citees, burghes, castels, hye toures,

Thropes, bernes, shipnes, dayeryes

This maketh that ther ben no fayereyes

While these verses should not be understood as representative of the whole medieval christian worldview, they help understand how medieval Christian generally understood the world of their daily life as essentially "normal" in comparison to the the fantastic world of the past or of distant lands. To my knowledge there is no instance of a mention of dragon as a creature which could be observed in the "common world" of medieval people.

In other words while these people believed in dragon as existing in some ways, they did not believe in them as existing in the same time and place as them. We may compare that belief with modern beliefs in alien beings. Many people believe in alien civilization without thinking much about it. They absolutely not expect to see an alien and would perhaps not even believe their own eyes if they saw one.

As for your question regarding when did people stopped believe in them. I don't know, others have certainly a better insight on this topic.