Does PE do the VC thing where they buy 10 or 20 things expecting 1 or 2 to hit big and the rest to fail? If so, they're placing a bet, but if it's not promising they'll let it die on the vine.
Also, VC returns are distributed according to a power law because most startups won't pan out. Private equity buys companies later in their lifecycle, banking on levering up stable operating cashflow rather than banking on the product becoming the next FAANG unicorn. There's a bit of a continuum between VC -> Growth Equity -> Private Equity.
Their MO is more like (1) take something that is basically working but needs capital (2) work out a deal that gives them a enough leverage (e.g. board input/control, debt financing pressure, etc.) then (3) squeeze it for a quickish exit for the PE and (4) move on to the next.
Doesn't always work, of course, but that's the playbook.
Of course the flip side of that is sometimes, particularly with a young company, they just don't know what the hell they are doing. A PE company could potentially fix some of that, potentially at a reasonable cost.
One way to perhaps think of it is this: VC types are in the business of betting on people, and don't necessarily trust the product. PE types are in the business of betting on products, and don't necessarily trust the people.