What is to be made of "e" ending so many Middle English words?

Solution 1:

The simplest explanation is that it’s a simple case of phonetic changes buggering up what used to be sensible orthography.

In Old English and earlier Middle English, some words ended in a consonant, while others had an extra, final, unstressed vowel: in Old English, just about any vowel could serve (though -y was rare), while later on, most of these unstressed vowels merged and were pronounced the same, probably as some kind of schwa [ə], most commonly associated with a weak form of the letter ⟨e⟩ in particular (perhaps because that’s how the final schwa was written in Old French around the same time).

When that happened, it’s only natural that the scribes of the time started faltering and getting unsure of which words had an ⟨e⟩ all along (and therefore didn’t change), and which ones used to be written with ⟨a⟩, ⟨i⟩, ⟨o⟩, or ⟨u⟩. The system was gone, and suddenly you had an enormous chunk of words and case forms that all ended in [ə], but were written in half a dozen different ways.

Eventually, this synchronically random system was of course abandoned, and they started just writing ⟨e⟩ everywhere.

But what happens, then, when a few centuries later, that final [ə] has been whittled away at for so long that it, too, has completely disappeared? Back when the schwa was pronounced, it was obvious why you wrote an yong man [ən joŋ maːn] but the yonge man [ðe(ː) joŋə maːn]: they were different words, pronounced differently, so of course they were also spelt differently. But once they’re both pronounced the same, [joŋ], but still spelt differently, you’ve got a nice, fertile ground in which to start sowing confusion.

This was around the same time that popular (by which I mean non-ecclesiastical, vernacular) literature and writing started spreading far beyond what it had previously been, so you had a whole new group of people writing the language that had never been thoroughly trained for years as scribes—they just wrote what they spoke.

After a while of this, you’d quite naturally end up with a kind of written diglossia: the untrained who wrote how they spoke would be more likely to just leave off all those pesky little -e’s (that weren’t pronounced anyway) and just write what they pronounced; while the more thoroughly trained scribes who had historical documents at hand and had been taught Old English (not to mention Latin and probably Old French) grammar would be much more likely to maintain a more conservative, archaising style, effectively creating a ‘high-brow’ literary style that would seem, among other things, to be characterised by an abundance of words ending in some mysterious -e that meant absolutely nothing and wasn’t pronounced.

Just like nowadays, when people tend to use fancy words to sound clever (even if they don’t understand them and end up misspelling and/or misusing them), it would of course be desirable for an untrained writer to appear more high-brow and literary than he perhaps really was—but since an untrained writer had no real way of knowing exactly where to stuff in all these pesky extra -e’s, it’s almost unavoidable that he would start adding them, well, more or less at random. When he felt like it.

Once the untrained writers started significantly outnumbering the trained ones, the not-so-systematical system of optionally adding silent -e’s at the end of many words became the standard practice. At some point, even the trained scholars gave up and just went with it—that’s around the time when writers like Ye Olde Robert and later on Shakespeare start to enter the stage.

(Actually, Robert himself was probably on the stage while the schwas started to be deleted, which seems to have been a process underway by Chaucer’s time, about 30 or so years after Robert’s reign. But whoever wrote down the text you were reading might well have done so later in the century, so it’s roughly around the same time.)