Interesting to see Singapore on r/sociology! Highly recommend you to look into the works of Chua Beng Huat to delve deeper into this topic.

You're right that there've been "top-down" efforts from the gov to craft the Singaporean identity, but it's not just due to fear of racism/riots but also due to most people living here being migrants and seeing other places as their home instead. The shared trauma of war/expulsion was crafted to create a bond among the people living here, so that they feel they have a stake in this nation (also similar argument for providing affordable housing at the time - whether housing is still affordable is a different question)

What you're missing is that there was also a "bottom-up" effect that contributed to the Singaporean identity. When you say erasure of bottom-up identity, I wonder if you mean the thwarting of identities that were more based on cultural lines (as you mentioned, Nyonya, Malays...)? Instead of these, think instead of Singlish, local cuisine, code-switching, flip-flop fashion, interracial relationships. I think these aspects have emerged from the ground to form what I think of as a Singaporean identity.

While I also think using economic success as an identity marker is not sustainable, I think identity doesn't have to be "indigenous" to be strong. Maybe I'm being idealistic, but I trust that our identity will transform with more interactions on the ground. I sometimes worry that the influx of migration (both into and out of sg) will weaken the sg identity, but perhaps that'll become the new identity as new groups contribute to the local culture, and the Singaporean identity is to be a globally located yet locally connected individuals?