https://www.ft.com/content/38b297b4-5b96-11e9-9dde-7aedca0a081a
1) They rejected His deal because he had ample opportunity before this to be part of the pre-pack administration team and refused to do so:
The first was that he was a shareholder rather than a creditor. Chris Wootton, Sports Direct’s deputy chief financial officer, said the company had been invited to join a creditor group led by hedge fund Silver Point Capital last summer. But it declined to take part in what it believed would be a carve-up of Debenhams.
2) Due to him not being part of the admin team his offers of earlier "loans" were rejected as he is not considered a creditor
Debenhams persuaded Mr Ashley to sign a non-disclosure agreement — legally making Sports Direct a party to ongoing refinancing talks and precluding it from buying debt in the market. “He should have bought into the debt before Christmas. That was a big strategic mistake,” said the restructuring expert.
3) Despite Ashley's beliefs, Debenhams appointed highly regarded and expert teams to work through the administration, Ashley offers nothing but his "personal team"
Debenhams and its creditors assembled heavyweight advisers, including investment bank Lazard, lawyers Freshfields and Kirkland & Ellis and boutique firms Houlihan Lokey and FTI Consulting, for whom complex restructurings are meat and drink.
Mr Ashley relied more on his trusted internal team. “Mike is disdainful of highly-remunerated advisers, but when you’re dealing with people who do this sort of thing week in, week out, it helps to have expertise in your corner,” said a partner at another restructuring firm. Sports Direct said this had no effect on the outcome.
4) Ashley wanted complete control over the company and is a much larger long term danger to the business in contrast to a professional administration team
Mr Ashley’s unpredictability was also a factor. In recent weeks Sports Direct has described the pre-pack as “a long-planned theft”, said that Debenhams advisers should be sent to prison and called for its executives take lie detector tests.
Described by one person familiar with the negotiations as “hand-grenade tactics”, such outbursts created an atmosphere of mistrust. FTI, which also acted as administrators, cited Sports Direct’s call for a shareholder meeting to dismiss almost all of Debenhams’ directors as a major reason for not trying to sell the company as a going concern.
5) Ashley has offered slowly increasing offers to "help" Debenhams £40m, £60m, £150m, £200m. It really needs its entire debt to be cleaned which is £520m. This doesn't preclude any existing loss making stores that will need to be restructured or closed too.
He could yet buy Debenhams — the administrator is obliged to conduct a formal marketing process — although he would have to pay off its £520m of debts and inject working capital.
In conclusion, if Ashley genuinely wanted the company he could have been part of it from the beginning but refused to work alongside the other administrators by buying in. If Ashley does want the company he can probably buy it in future after the restructuring if he so wishes and makes a compelling offer.
Shareholders may have lost out, but they will have lost out anyway, allowing Ashley to take over the company wouldn't of saved the other shareholders money, it would have just allowed Ashley to rake back most of his own money through asset stripping and moving the brand names back to his home company of Sports Direct (see Dunlop etc..)
Directors will have not agreed to the buy out simply due to him wanting to fire them all, so it certainly wasn't in their interest to accept that.
Employees may be sceptical about working practices under Mike Ashley (anyone remember the Sports direct scandal a few years ago) so perhaps they wouldn't want him to take control either.
Creditors as explained above didn't want to allow Ashley to take control as he refused to be a part of their collaborative effort from the beginning and his untrustworthy and unpredictable behaviour does not generate a belief that it is going to result in a sustainable future, nor is it likely to increase the chance of them retrieving any of their debts owed.
That is three internal stakeholders and the creditors with clear reasons to reject his offers. Creditors can probably be convinced should he wish to take on the ENTIRETY of the debt and you could probably convince directors if he had a better attitude and wanted to work with them rather than fire them all.
Instead of offering such things Ashley has decided to threaten to mount a "legal challenge" because they rejected him. Not really the sort of actions of someone who is trying to work to save a company over his own self interest.