Yes, sadly the 1990s was a time of consolidation through leveraging assets. Same thing happened to the company I worked at in the 1990s. The founder who was very debt adverse died. New management came in and immediately leveraged our assets to go on a buying spree of similar companies. The burden of that debt forced them to eventually sell off there original building from the 60s and led to the company being taken private by a private equity group some 15 years after this mess started so the debt can be finally cleaned up without analysts second guessing every move.
Companies did it because at the time the stock market wanted to see top line growth and acquisition was looked at as growth. It was the only thing analysts looked at and rewarded. Large chunks of the cost of acquisitions could be written off, offsetting the debt with "goodwill". Then accounting rules changed and companies balance sheets went from looking great to terrible overnight, stock prices plummeted and the management responsible got sacked.
In the case of AMPAD, Bain bought them in 92 and took them public again in 95 or 96. When the company went bankrupt in 2000 Bain still owned a 1/3rd of the company and lost quite a bit of money. But AMPAD survived bankruptcy and is now owned, after a string of owners to Esselite, a private company who owns a number of office supply companies.
And same is true with the other companies you listed. Over leveraging for acquisitions in the 90s led to major problems when accounting rules changed which led to their downfall. But you got to look at the good with the bad. Success stories with Staples, Dunkin Donuts, Burger King. Toys R Us would be gone without Bain Capital and KKR buying them in 2005.