Question about tax

Ive been struggling to wrap my head around the topic of tax when it comes to cryptocurrency. In alot of contries, every transaction between different coins is taxable.

Scenario 1: I purchase Bitcoin for 100 Fiat. Value increases 50x and is worth 5000 Fiat, at which point I trade my Bitcoin for Monero. This will then be a taxable event and I owe the taxman say 25% of the profits, 1125 Fiat. A year later, Monero drops 99% and Im left with a value equivalent of 50 Fiat.

In total, a 100 Fiat investment turned out to cost 1225, well minus the 50 you are stuck with in your shitcoin.

Am I getting something wrong here, or is this a possible scenario?

Scenario 2: I purchase bitcoin for 50 Fiat and Monero for 50 Fiat on day 1. Both 50x in value, and are worth 2500 Fiat each. I convert my Monero to Bitcoin, and taxman claims 25% of that. So im left with Bitcoin worth 2500 fiat + 1887.5 fiat, instead of the flat 5000 if I went 100% bitcoin on day 1? (Well obviously I still keep my bitcoin, but have to pay Fiat equivalent of that amount).

Would it not make more sense to simply get taxed when you make transfers back to fiat? Does it generally work the same way with taxation of stock investment?

Thanks for any serious answer, im rather confused about the whole topic, and obviously need to read up on it.