Can someone ELI5 the HISD takeover?

I’m a damn teacher (another district) and I don’t understand how HISD as a B (88%) rated district is on the verge of being taken over by the state…

Cy-Fair is an A (90%) Klein is a B (88%) Aldine is a C (77%)

And I keep seeing about the failure of Wheatley high school in previous years…but

So what’s the REAL reason??