RM is strongest since 2018. What about before 2018?

Malaysia has yet to reach the levels we were in before 2018. We do not need to go even further but suffice to say, that I personally do believe countries which has trade surplus should have a stronger currency while countries with a big deficit should have a weaker currency. This is how the trade balance is remedied. When Malaysia is exporting, the country which is importing would pay us in RM. So, of course demand for RM should increase and this should support the value. I know, this sounds simple. Else, please tell me how and why do currencies fluctuate then? For the purpose of speculative investment? Hmm….