My wife's job (before she retired) was managing applications for European funding and funding reviews.
If you read the reasons given in the assessment and understand the way EU projects work the reasons given tell you what was missing from the application.
In general the EU likes collaborative projects - groups of companies in different countries all coming together to work on one project with a clear economic benefit. Sceptics say it's so reviewers get to travel to a wider range of exotic destinations Everyone wants to partner with companies in say Venice or Nice.
The art of creating such a project it to find companies whose pet interests can be convincingly portrayed as fitting into one seemingly cohesive project. This can be difficult.
Since i worked in the same industry as my wife our paths ocasionally crossed at review meetings. On one occasion my boss told his new secretary to book me a flight and a hotel room in Paris adding with a wink that "Colin will need a double room". She knew I was married but not what my a wife did for a living, we left her thinking I had a mistress in Paris for a few hours before telling her.
A motive very on the same lines was given to me for rejecting the idea of even submitting a proposal to this call, by an Italian researcher. He said that a good portion of the budget would only be for bureaucrats going to good hotels.