I am sure that Singapore had standing plans for an ongoing modernization of it's mechanized and armored forces.
There is a correlation but
correlation is not causation.
The SAF typically has a long term plan for modernization. The first thing to change is doctrine and changes to weapon systems will be made in conjunction with the doctrine change. Once we 'prove' through trials that a concept works, the program for acquisition beings (typically a 2 to 4 year cycle). It will not be rushed and and it will not be an ad hoc reactive decision (though we are known to conduct reviews* based on new inputs). We are very interested in new capabilities and new platforms are a product of our desire for capability enhancement.
I was involved in certain trials in the late 1980s and we have only recently declassified aspects of those trials now called the Army 2000 project. I can tell you certain weapon platforms that were introduced in the 1990s were the result of decisions made in the 1980s.
But I also think that the news of Malaysia procuring the PTs and the nearly immediate availability of the surplus Leos made it easy for Singapore to make a fast decision about the procurement.
IMHO, there has been unrelenting pressure by the army to upgrade our equipment and the Leo 2A4 acquisition is part of the pressure we put on Mindef and the minister. Please note that all the necessary support equipment were acquired or designed before the Leo 2A4 acquisition (Bronco fuel resupply vehicles, M3 and even our VLBs). It has been recently announced that we will upgrade armour protection for the Leo 2A4 and the weight increase was catered for by prior planning.
The reason we are so happy with the PT-91M purchase (it is a MBT after all), is that once that occurred and there was no need to 'hide' our Leo 2A4 acquisition.
Singapore is politically sensitive in relation to any 'offensive' equipment acquisition to avoid protests in Malaysia (on our offensive capabilities). Even a
book on the SAF affected Malaysia-Singapore relations.
Sorry about the long reply to a single point.
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* Singapore was offered the F-18, when Malaysia and Thailand (order cancelled) placed orders. We reviewed our decision and went ahead with our 20x F-16 block 52+ (or F-16I) purchase.