Hollywood was rocked when one of its most lovable couples, DANNY DEVITO and RHEA PERLMAN, announced out of the blue that they were separating after 30 years of marriage!

The big question on everyone’s lips was, “WHY?

Only The ENQUIRER has the answer as our exclusive in-depth investigation takes readers behind the scenes of the broken union.

“Rhea had hoped they’d spend their golden years enjoying long trips together, being with family and doing an occasional film or stage project,” lamented one insider.

 “But now she has decided to start a new life on her own.”

Ironically, Danny’s hit FX show “It’s Always Sunny in Philadelphia,” played a role in the split. While helping to revitalize the 67-year-old actor’s career, we reveal how it strained his domestic life with 64-year-old Rhea, who shot to fame on the now classic sitcom “Cheers.”

Sources told us that Danny also had a wandering eye for the ladies, including friends of 29-year-old Lucy, the eldest of the couple’s three grown children.

 And we unveil the reason why Danny’s summertime stint in London starring in a stage production of “The Sunshine Boys” may have been the final straw for frustrated Rhea.

You can find ALL the details about the shocking separation in the new ENQUIRER, the Number One source for in-depth celebrity news!