Keeping USDT is like keeping FIAT, you cannot grow your investment with FIAT in crypto.
However, the concept of USDT or TUSD comes handy when you are going short on Bitcoin, if you are expecting a bear trend in the market, its good to convert your sats in usdt and buy back sats again from USDT, in that way you increase your Satoshi holdings and in turn your BTC value.
In investment it is not good just to keep for long rather try to invest again in another form so that the money you will gain will only round in the system. Not to afraid but trust yourself in any form so that you will stand firm. Bitcoin is good and a lot of advantages that brings into the life that is the reason why they keep it for long.
I believe you are right, investing in several forms give us chances of profits in numerous forums
And it brings hope because when a project fails, another prospers
But still, accumulating more satoshi is the best in this bearish period
Always