Barcelona knew what will happen if they allow Atletico Madrid get all 3pt and it would have been game over because the 3 teams won't want to lose and drop point while hoping for others to make that mistake. I don't think the champions league game they lost to Madrid was the cause of what killed Atletico Madrid's morale, they were over confidence after leading by 2 goals against Barcelona and that's bad if you're playing against Barcelona who are also fighting to get that top spot and secure the 3pt, you go all out to give your best and also defend more too, they should have continue to press and defending just like they did to Bayer Leverkusen but they failed. Barcelona will continue their good form till the last day, for now the whole thing is in the hands of the top 3 teams.
If Atletico Madrid had won against Barcelona, Real Madrid would have been at the top of the table and Atletico Madrid would have been 1 point behind in the second place. But Barcelona performed brilliantly and secured 3 points. Despite playing one match less than Real Madrid, Barcelona is on the same points table as Madrid.
Atletico Madrid is now far behind in the title race due to losing the last two matches. If Barcelona wins their next match, Atletico Madrid will be ahead of them by 7 points. This is a very big gap at the moment. So I would say that Atletico Madrid has already been eliminated from the title race. Now the fight will be between Barcelona and Real Madrid.