[IKE]

I will jump to what I believe could be root cause. In your scenario (which is not terribly unique), I think the team was missing "its culture" or core values. Without a core culture, many things can step in and become the core culture, and these shifts can cause a lot of agitation and disruption.

Sometimes this can occur when a team gets new leadership. Often it is when a core person leaves and there is a void (in talent, skill set, or personality).

Sudden success can be a double edged sword. It often comes with a lot of positives, but many negatives can also follow like the "want to win" overriding some peoples beliefs of what the "team", and "program" should be.

Deciding on and following core values can be incredibly important to the stability of a team, but is an often overlooked step.

Most successful teams I know of would value the experience of "the team" over the experience of a particular individual (a student included), however they would also agree that the students should be getting inspiration and improving skills if they are willing to put in the effort. Most of them use some balance in involvement, engagement, and responsibility with the results they want the team to have. This does not mean the project should be all smiles and high fives. FRC is a tough competition. The scope and time commitments are difficult on all involved. Teams and individuals will have bad days, possibly even bad weeks or competitions, and sometimes even bad seasons. With a strong core, teams can bounce back. Without developing a strong core, then teams will tend to bounce around between highs and lows. This is the same with any organization (and often the same with any individual entity).