Laker's business model was not sustainable and his airline was going rapidly down the tubes. McDonnell Douglas and General Electric put together a rescue package and the 'conspiracy', which was real enough, consisted of a number of flag carriers (led by BCal) warning them off.
The "rescue package" included McDonnell Douglas become a shareholder in Laker. The "warning-off" was other McDonnel Douglas customers telling McD that it would be very difficult to buy any more aircraft from them as this would involve discussing confidential information with a shareholder in a rival airline.
The Laker story will always be coloured by the myth that he was a good businessman. Obviously he was not! As well as buying a fleet of A300s for routes without licences (as mentioned by SSK) his original DC-10 order was for Skytrain - which then took about five years to get approval from the US. For those five years he was desperately trying to find work for his aircraft!
Regarding Lofleidir - they were successful as they were not members of IATA which at that time was a price-fixing cartel. Once price-fixing by IATA was banned Loftleidir lost a lot of their commercial advantage.