Europe is finally acknowledging the cancerous existence in their midst...called terrorism. The authorities are no longer turning a blind eye and a deaf ear and have come down on the perpetrators hard. They are communicating with other governments in the attempt at intelligence sharing. Well, it is finally working. The sore is no longer being allowed to fester, instead they are being excised slowly but surely.
Although many terror attacks were foiled in Europe this year, the total number of terror attacks that occurred exceeded previous years. Without all of the information about the number to attacks which did occur, one cannot say whether Europe is doing a good job of tracking terrorists recently or not.
This could mean the terrorist organization is concentrating elsewhere; in another place either they have never attacked before, other a place they find more valuable. Just because a country is seeing a decrease in terrorist activity, it does not mean the country has done better defending its citizens against the threat.
The terrorists are recruiting people who are sloppy at what they do. This is a good thing as it makes them easier to find and stop. This is not necessarily indicative of a heightening of skill on behalf of law enforcement. They are just stumbling upon inept terrorist groups always.