Not sure how Malaysia does it but my experience in Saigon was that the United Airlines flight I was boarding’s final destination was USA (even though I’d be changing planes in Hong Kong) and because of that we had to remove shoes and go through the same procedures that are done in US airports.
There was another flight boarding whose final destination was not USA and those passengers did not have to remove shoes. Not sure if it was a domestic flight or an international non-US flight.
I also remember the announcement for my flight and they said that because the aircraft would be flying to the US that passengers would need to remove shoes...etc.
I’ve gone through a lot of European destinations where nobody, American or not has, to remove their shoes. And in any case, I would doubt that this was a shoe bomb, especially if there were 4 passengers aboard with false passports.
My suspicion is that the four had smuggled explosives and had actually planned to detonate the plane elsewhere or perhaps fly it elsewhere and take out some other target, but that they just blew up too soon.
I’ve never flown to Asia, so I don’t know their procedures. This is just a comment as a fairly frequent flyer.