The truth of the matter is that a surprisingly large fraction of basic research funding is spent more on "heads" than "ideas" anyway. First of all, you have personal grants (such as the ERC Advanced Grant) or sponsored professorships (such as this one). While these will typically require that the candidate defines some project, at least 50% of the evaluation is not of the project, but of the past success and future promise of the candidate. It is easy to argue that these funding schemes are betting much more on people than on the specific project.
Further, even for "normal" basic science projects, one typically has significant freedom in how to actually execute the project (to the extent that one not infrequently ends up running a completely different project than what has been pitched originally). Funding agencies of course know this, and are often willing to grant a strong applicant with a weakly developed idea money, where they would almost certainly refuse a weaker applicant with the same research proposal. This is again the same basic idea - for a strong applicant, they may assume that they will do something useful with the money (even if the currently pitched problem seems not well developed), whereas they won't give the same benefit of doubt to a weaker candidate. Again, they are betting more on heads than on projects (also because at the end of the day in your typical basic science open project call, they don't really care about the specifics of any project - they only care that good science is done).
There is, of course, an annoying flipside to this. Namely that it leads to a "the rich getting richer" effect that is very hard to overcome for less established researchers. For grants such as ERC you are basically out of the running if you are not already among the best in the world in your field, and even for smaller project grants an inexperienced researcher will often need an outstanding idea to be able to compete with all the researchers with established credentials (who, of course, typically have good proposals in addition to a better track record).