I have a few things to point out, and I'm going to keep them as short as possible:
1. Picture this: Toon Link has a bomb in his hand. It is a projectile, but it's now really difficult for him to hit you with an aerial or set up any sort of real 'pressure' at this point without getting rid of the bomb, or dropping and then catching the bomb again via aerial, or going for a ZAir. I'm a little fuzzy in regards to item mechanics in this game, but for the person you played against, this holds true. He did not attack you with anything threatening while bombs were pulled. He tossed them, dropped them, and then proceeded to set up legitimate pressure.
2. Everytime the player pulled a bomb, you rolled away, giving up a massive amount of stage control. That exchange of actions repeated itself multiple times throughout the set (watch the video again.) Why? You were giving him free space to work with due to a bomb pull. Think about that. When he tried to pull a bomb or toss it, he would frequently go into a short-hop, or double-jump to pull/toss them. Jumping in this game gives up a lot of ground control and puts you at a disadvantage (for most characters). You attempted to chase him down, but gave up on the effort midway. You never considered approaching with an aerial or an instant item toss when he opted to toss a bomb at you. If you chose either of those options, the bomb would have been caught, and you either would have thrown an attack out at the same time, or threw the bomb somewhere. You can't give control of the stage up like that, especially if he's just going to jump around.
3. Following up on what Luminaire said, you played pretty well for half of game 1, and then just lost your composure after losing your stock. I'm not sure what happened, but that won't do. When playing against someone, even if the character matchup or player matchup is mentally taxing, you really shouldn't switch up if you don't need to. If something was working for you for the first minute, why not keep using it? If you aren't given a reason to think otherwise, or a reason to adapt, you don't need to do anything. I am 100% certain that you lost that set due to yourself. You mentioned it yourself in the post that you went in there "expecting to lose", which is something you need to stop doing. Either expect to perform to the best of your ability, or don't expect anything at all when you play (I do the latter, if anyone is curious). Expecting a negative outcome is only going to hinder your play, and cause you to under-perform. That's all I'm going to say on that.
Adding more onto what Luminaire said, there was a lot of pressure, but it was extremely linear (bomb toss -> aerial with a very rare grab attempt mixed in). If you had just walked forward and held your ground, you would have been fine.
4. When you were close to him and you had your shield up, you used the auto-pilot Bowser option: Spotdodge -> UpB. I won't tell you to cut that out, because you did get him with it the first two times, but he adapted and just figured out that if he held his shield for about half a second longer, he would block the Up-B and punish you for it. Like I mentioned when I did that massive critique of your first batch of videos you posted, you have to really consider what options you're choosing when you're in a situation like that--especially when your opponent is beginning to adapt to the option you have chosen.
5. Don't forget the universal options you have in this game. I'm referring to short hop airdodge cancels with this statement. I'm not sure how useful it would have been, but you have to experiment with certain things to see what your opponent is and is not receptive to.
edit: thinking about it now, it would've been very useful. In fact, I actually made a post about an instant toss OS in this game that exists due to short hop airdodge canceling now that I remember. I'm too lazy to find the link, so I'll explain it briefly: put in the inputs for an instant item toss (airdodge + cstick direction) and then buffer a special move to cover both options. If the item comes near you, you toss it somewhere. If not, your special move comes out.
You did play different in the first and second game. As I mentioned above, the first half of the first game was very promising. Even though a few mistakes were made, it was still early, and you held your ground and were able to keep up with him. Then you became too impatient--I'm not sure if you just fell back on autopilot or what, but it became evident by game 2 that you had stopped trying to adapt to what he was doing. Your opponent became stuck on the same linear style of pressure because it was working.