I was also surprised by how well these two teams did in the Europa League, especially compared to how they did in the Premier League.
I'm looking forward to the match between United and Lyon and as a United fan, I hope they will win but I don’t have the psychology to be so arrogant, the club has the mentality of a wet dishcloth. United should just be ready to fight for every game as it comes
As for the match between Tottenham and Frankfurt, IMO it is 50/50, especially after Frankfurt's last match. The penalty shootout will decide the final result.
The unpredictability that comes with supporting Manchester United can actually be humbling and I understand it clearly when you mentioned that you don't have the psychology to be arrogant about the team as they may disappoint later. It even feels like Manchester United and the spurs appears to be suffering same fate, you cannot bank on the spurs aswell both in the Premier League and in the Europa, it's been a season of too many uncertainties for both team but let's keep our fingers crossed as see what they have got with the europa while hoping for the best.
That's my plan... I'll hope for the best, but I won't be surprised or disappointed if United doesn't make it to the semi-finals.

United has what it takes to reach the semi-finals, but they need to be careful, Lyon will not be easy to beat!
Lyon has the talent and tactical discipline to cause United problems, especially if they can exploit defensive weaknesses. If they can stay compact, counter-attack, and take their chances, they have a chance to pull off a statement win
Whatever happens, the match between Manchester United and Lyon is going to be a spectacular clash. IMO
I wouldn't conclude that Lyon will win the match because they are not an English club. United performance against a team that's not in EPL is unpredictable because we might think that they will perform poorly and it will be the opposite. In the round of 16, nobody will believe that United would win the match with a good goal margin, because they were all saying that Real Sociedad has professional players. I will not underestimate United because of their current form.