The reason why bus operations are profitable in Hong Kong was that the buses are filled full on commuter services for the fixed cost, such that urban services, which are generally unprofitable on its own due to increased congestion, can be provided at marginal cost only with fares attractive to short-haul passengers taking a few stops only. Here, commuter services can be replaced with school services in most part of the country.
The reason why commuter service is profitable is the speed as driver cost is the most significant portion of bus operation, and by running buses fast on motorways, bus service can be provided at a speed comparable to driving at a ticket price much cheaper than car cost, while providing a profit to the bus operator.
In London, due to the lack of motorways, bus services are never going to be attractive to long-haul passengers, unless they are forced to take it to get across places where there aren't direct rail connections. The reliance on railways in London is much more than in Hong Kong as, in Hong Kong, motorway buses (which charges much more than short-haul urban buses, but the operating costs per hour are similar) can be an attractive substitute for long-distance passengers where there is no direct rail connection, but here in London, it is almost always better off to switch to the railway at some point during a long-distance journey.
The over-reliance on Victorian-era railways, combined with the lack of orbital railways / motorways, in London has made all railways into London city centre overcrowded in peak hours (at least before COVID) and turned London into a standstill when the railways fail, e.g. the Tube strike happened recently, but the opposition to motorway-building in the last few decades have resulted in this, where most other cities in the world have built many motorways on viaducts into the city centre.