Why has it taken the 75% of the shareholders so long to take this action? This should've happened 18 months ago at least. And surely they'd have seen the accounts before being filed to Companies House?
As a general rule, no they wouldn't have advance sight of accounts before filing unless they were "insiders" to the company, such as a shareholder who is also either a director or manager. As an (essentially passive) investor in a limited liability company, you collectively get to appoint or remove the directors, but you don't usually get to see anything that the management don't want you to see, and except in exceptional circumstances you'd not have any right to. If you're a shareholder and you want that visibility, you make yourself a director.
Your argument that investors should have acted early is not necessarily a bad one, but as the shareholders were nominally responsible for appointing the directors in the first place (or buying into the company with them in place), it doesn't make sense to act precipitately. Look at those dismal football clubs that have vast turnover of managers, because they always dump them at the first run of lost matches - and yet they never do seem to appoint that winner who'll take them to Wembley. For better or worse, if you do ever want to win you do need to give the management time to perform, and when you're very clear that any change has to be better, that's the time to take the risk of change.
With the benefit of hindsight we might conclude they were wrong, but I don't think the shareholders were remiss in not acting earlier, given that it is now still only two years from the original invitation to crowdfund the Vega Plus.