That's not necessarily a problem.
All charities have to keep reserves - often 6-12 months of their running costs, so that they can continue to operate, or wind down some services slowly if needed (for example, lots of charities might run with grants from local authorities - most of which have been cutting services for over a decade now, and if they end a charity's funding, the Charity Commission doesn't want the charity to have to close overnight and leave the people they're helping high and dry).
You also have plenty of charities that are grant givers themselves. Something like the Bridge House Trust, which has been around for hundreds of years, was originally meant to keep a large reserve so that they could replace any bridges across the Thames if they collapsed. It now uses the money to give grants to lots of smaller charities. It has well over a billion pounds in assets, which it invests, and they can award many millions of pounds in grants each year from the profits.