Directors resign for all sorts of reasons, Tali1. In some cases a limited company is created purely to sell on later. e.g. firms such as this one register thousands of companies as 'general traders' (or similar) and then change the names of those companies to order when someone wants to acquire a limited company in a fuss-free way:
https://www.1stformations.co.uk/
[In case I've not made that clear, businesses like 1st Formations set up thousands of companies called, for example, 1st Form Number 1 Ltd, 1st Form Number 2 Ltd, etc, with articles of governance which say that they can do everything from selling fruit and veg to carrying out space research. If you want to set up 'Tali 1 Super Bargains Ltd', 1st Formations will sell you '1st Form Number 987 Ltd' but change the name of that company to your chosen one as they do so].
So there will the resignation of at least one director even before the 'real' company comes into existence. (i.e. the owner of 1st Formations will resign as a director of 1st Form Number 987 Ltd when he sells it to you and it becomes Tali1 Super Bargains Ltd. His directorship will still show up, as 'resigned' when anyone looks up the details of Tali1 Super Bargains Ltd).
At other times a prominent businessman might be paid a fee to allow his name to appear on the list of the board of directors of a new company to encourage investment, even though he's not planning to remain as a director for any length of time. (e.g. if you were seeking investors to put money into your new company, it would look good if you could honestly say that Richard Branson was a director. You wouldn't need to declare that he'd said that he'd be resigning after just a few months).
If a business is doing particularly well, the directors might decide that it's a good time to sell it, so that they can make a quick buck (especially if, as with many small businesses, they own all of the shares in the company). In which case, when they relinquish control of the business, all of their names will then show as 'resigned'.
Exactly the same is true of a business which the owners want to get rid of because it's not making any money though. So a long list of resignations doesn't necessarily mean that a business has either been doing particularly well or particularly badly.
Other directors might resign because they've no longer got the time to run the business or, say, for health reasons.
A few directors are forced to resign because a court bars them from holding directorships.
There are many other reasons why a director might resign. In trying to work out whether a business is likely to be 'kosher' or not, I tend to concentrate on the backgrounds of the existing directors, rather than on the number of directors who've resigned. For example, if clicking on the name of a director of 'Super Great Double Glazing Limited' shows that he was previously a director of 15 other double-glazing companies, all of which have ceased trading, as well as being a director of another 6 double-glazing companies, all of which have overdue accounts, I probably won't be ordering my double-glazing from his business!