I would have very great difficulty in believing this was a sincere offer at normal co-operation between 2 airlines.
It's a bit like a tobacco company offering to sponsor sports events for children as long as they take place in an arena covered in cigarette adverts.
It is in Ryanair's interest to keep Alitalia alive but on a life support system. Still alive so Ryanair can claim they don't have a monopoly in Italy, but too weak to challenge Ryanair in any meaningful way. If you've ever seen a film of adult killer whales playing with baby seals, you'll know what I mean