Although this may not be a LBO situation, selling junk bonds is often the way that PE firms steal everything from firms they "buy". I have no idea how the "all-stock" claims jive with selling bonds. I suppose the buyer could just issue more of its own stock, if the numbers don't add up. [EDIT:] This last maneuver seems more plausible if the buyer itself was previously a LBO target and the PE dudes haven't totally drained it yet.
How is taking on debt, relevant to an all-stock deal? An all-stock deal means that Grubhub shareholders aren't receiving any cash, they are receiving $7.3B worth of JustEatTakeaway stock.
The only interpretation I can think of, is what the previous poster said - the existing shareholders of JET are getting significantly diluted
"Just Eat Takeaway was created this year through the $7.8 billion combination of two of the earliest participants in Europe’s food-delivery market, Just Eat and Takeaway.com. It has been fighting competition in Europe from Uber Eats and Deliveroo, a London-based company whose investors include Amazon.
Mr. Groen, a Dutch entrepreneur, founded Takeaway.com in 2000 when he was a student frustrated with the challenge of ordering pizza online. He took Takeaway.com public in 2016, and now has a net worth of more than $1.5 billion, according to Forbes.
In addition to the deals for Grubhub and Just Eat, Mr. Groen bought the German portion of Delivery Hero’s business for about $1 billion in 2018."
They've been aggressively acquiring competitors for years, so this seems par for the course.