You're right. One of the reasons why is it's the most popular is because it is the first ever cryptocurrency. Also because it took time before altcoins emerged, that's why for a long time Bitcoin has the spotlight, getting all the media attention. But it's slowly changing now as altcoins are getting better and better.

According to me the bitcoin being the most trusted digital currency as it is adopted by many nations and other coins are a just scam or the game of few days.

Doge coin was (is?) actually a joke coin where the developers made it just for fun. The coin ended up surviving till today thanks to the active community and the developers.
You answered your own question.

There's more to it, I think, since there are other altcoins which gained some popularity right after Bitcoin was first released.
The difference is that they still lack the infrastructure around them, they have almost no merchants accepting them outside of the crypto-sphere.

You could say that Bitcoin is slowly losing its dominance, especially when you look at the market cap of Bitcoin vs altcoins (ETH), but that has more to do with speculation than anything else imo.

After the price of bitcoin began to fall, the price of all crypto currencies, too, began to fall. Why falling bitcoin price to clear. 've all heard the pessimistic scenario, 1 Aug. Why, then price (ETH) fell too. This suggests that bitcoin is still a crypto currency № 1.

Bitcoin is 100% the most popular crypto because it was made before any other crypto had been developed (in the same way that Bitcoin was developed), if Bitcoin was to come out now it would be tossed aside because there would either be a coin that is more popular than it, and/or coins would have way better technology than Bitcoin and then there would simply be no reason to use Bitcoin.

To be completely fair, Bitcoin is great for what it does and my only issue is the fee/blocksize right now.

It seems that you already know the answer and you already answered your own question but just like to add up that many other crypto currency that is worth using for aside from bitcoin it's just bitcoin is the pioneer in this crypto currency world that is why it is so mainstream and it is the trademark of digital currency.

Many other coins offer more a lot of choices than bitcoin and much more cheaper and faster in sending transactions and there are also a lot of trust worthy crypto coins not only btc and doge.

I am sure the first thing that has made bitcoin popular is its value. The trend at which the value has stepped up over the years has made most newbies to start getting interested not just only in bitcoins but even other altcoins they can lay their hands on.
Secondly, bitcoin has been able to stand the test of time and I am sure it is gonna be unshakeable until we reach the moon. The recent adoption by most countries will definitely take it there.
Lastly, it remains the crypto king and the last time I checked kings are always popular in their world. It is the first and it ushered the way in for the birth of other cryptocurrencies, so there is no debate on why it shouldn't even be popular in the first place.

Bitcoin is the most popular of all the digital currencies because it is the first of them all. Without bitcoin, I don't think that there will be an emerging digital currency. Also, as the first and original digital currency,  it has the highest price of them all, so the tedency of the users are to be attracted to it because it has the most price.