Even though Mallorca finished in the top 10 last season, I've always considered them to be very weak against a popular team like Barcelona. Mallorca would always lose against Barcelona, and the best result for Mallorca would be a highly unlikely draw. However, I wouldn't underestimate a team like Mallorca this early in the season and would bet on BTTS (Yes) to get more decent odds.
You considered Mallorca to be a very weak team and still went on to play them to score Barcelona hoping to get a BTS for a 1.70 odds from a Mallorca team that is well known to be a rather defensive side than an attacking. However, it's obvious you lost this bet even before the game started as Barcelona defeated Mallorca on 3 goals to nothing for Mallorca, a two red cards on Mallorca players therefore making the victory a much easy one for Barcelona.