In bitcoin we do not have method than we can double our bitcoin safely we always need to take a risk to earn profit but we can reduce the risk we have by investing multiple, bitcoin has more method to invest then we need to try it all to earn more profit.
Investing on multiple or single platforms wont reduce the risk unless all of them are safe, because even if you invest in one place that is quite safe you will still stay safe but even if you invest in multiple places but some of them are suspicious then it is not recommended.
That's not what it meant, when you say investing in multiple platforms or commonly known as diversifying our investment it will only ensure that our journey in investing will last, as when one industry or an asset will not succeed you can still go on with your other investment and the possibility will happen that you will be able to recover your loses.