First I want to say this is sad news to hear, and my best wished to all crews and passengers effected. It's quite sad indeed.
Having worked with ex Monarch guys who fled the sinking ship in time, there is a couple of things that comes to mind.
Gross mis-management of the company. Their operating costs and crew efficiency must have been one of the worst in the business, management woke up to late to try to turn it around, and they was just never going to make it, nobody that I have met who left the last few years thought Monarch would ever recover, and the gave them max 5 years to survive.
I was told stories of amazing salaries and hardly any flights during 6 winter months, there is a saying if it seems to good to be true, it normally is something wrong.
The last years decision that the company had decided to swap from Airbus to Boeing, shows how mismanaged the company still was. The change the entire fleet from Airbus to Boeing was just an absurd action by management.
From 19.th of June this year
"Monarch Airlines today confirmed an order for 15 additional Boeing 737 MAX 8s worth $1.7 billion.
The order will expand Monarch’s 737 MAX fleet from 30 to 45 aircraft, with deliveries starting next year.
The additional new generation aircraft means that Monarch will have a completely new fleet by the end of 2022.
The aim is to transform the airline, the customer experience, its environmental impact and cost base, according to CEO Andrew Swaffield."
Surely great incompetence should come in to play here, I am sorry but this kind of "surprise" does not happen overnight. (Oh yes it did, doh....!)