Ok having now spent 11 days here in Malta I can safely say there's no place for Light Rail on the island of Malta. I'll do my best to explain why below.
1) The existing road infrastructure would be impaired by the presence of on-street running, and the net safety of the roads would be reduced.
The roads are, to put it politely, extremely challenging. There are large roundabouts in many places which help longer distance traffic flow, but there are also motorway-esque busy roads with sliproads sometimes joining into fast lanes. Merging lanes frequently merge slow-to-fast (which never appears in the UK), signage is often poor, and lane discipline is non-existant. The additional traffic from a metro can only be another safety concern.
2) Malta has an excellent existing transport network.
Despite the demise of Arriva on the island, the air conditioned bus network is prominent in all the built-up areas. Buses have dedicated lanes, priority traffic signalling, and Valetta bus station can rival many major light or heavy rail station in its ability to move people, and destinations served at all hours of the day. Don't let current (Oct 2021) Google Street View fool you - it has been redeveloped since the photos were taken.
There are rival electric mobility companies vying for dominance in the most built up areas. Bolt, the most prevalent e-scooter marque, serves Valetta, Floriana, Sliema, and even St Julian's in one contiguous area at a very reasonable price point.
The Sliema ferry is extremely popular, and a new terminal at the Sliema end is under construction. It doesn't currently take contactless payments or bikes, and isn't suitable for wheelchairs, but these are all to be addressed by the redevelopment.
The Gozo Channel line takes foot passengers at very reasonable rates, and there are bus stops with frequent services at both ends. Although the metro is not planned to reach Cirkewwa in the first instance, it would only replace a well used existing link if it did. Better to introduce integrated ticketing on both modes if possible.
3) The proposed routes (as I suspected) don't really represent the movements of people around the island, and likely are based on crayons over real loading.
People (read: those that I observed as a tourist, an admittedly small subset of all travellers) want to get in and out of Valetta at all hours of the day and night, and the existing bus network radiates from this focal point exactly as it should. This isn't an accident - it's where the passenger loading has encouraged buses to serve.