Other (probably more important, if combined) reasons :
wanting to have direct impact (i.e. risk aversion within longtermist interventions)
personal fit for founding (and specifically founding meta orgs, where impact is even harder to quantify)
not quite underfunding, but lack of funding diversity if your vision for the org differs from what OP is willing to fund at scale.
lack of founder-level talent
Other (probably more important, if combined) reasons :
wanting to have direct impact (i.e. risk aversion within longtermist interventions)
personal fit for founding (and specifically founding meta orgs, where impact is even harder to quantify)
not quite underfunding, but lack of funding diversity if your vision for the org differs from what OP is willing to fund at scale.
lack of founder-level talent