The source – support.google.com
Google Ads has made changes to matching keywords to search queries. Phrase matching can now be a higher priority than broad matching, regardless of ad ranking. The update is relevant in cases where a search query matches multiple keywords.
If there used to be a keyword with an exact match among the relevant keywords in the ads, Google Ads used it. But if there was no exact match keyword in the ads, but there were several relevant ones with broad and phrase matching, the system would choose the key with the highest ad ranking.
The first point remained in effect. The changes on the second point are due to the fact that Google Ads now takes relevancy signals into account. The system calculates the relevance of keywords to a search query based on the value of the search query, the value of all keywords in the ad group and the landing pages in the ad group.