There are plenty of acquisitions which I think are competitive, but the market conditions are the critical evaluation point.
Where this breaks down & this is something that the FTC needs to learn from the past (poor in retrospect) approvals and redress in the future is who the acquiring company is and how quickly they could bring something to scale which would stifle future competition.
When facebook acquired Instagram, it has ~900M MAUs and Instagram had ~30M MAUs (3-5M in just the last month or two before acquisition, accelerating very quickly). By facebook's own account their MAUs and growth rate was considered a threat, so they acquired them to remove the threat. Fast forward 14 years, Instagram has 3b MAUs and displacing them is going to be __very hard__.
If you were to apply that same retrospecitive lens to Google, they've been able to acquire Google Analytics, YouTube, DoubleClick, Android, Google Maps and others to take them to hyper scale, completely dominate a particular product space because of their existing massive user base.
Not an easy job for the FTC to get right, but (in my opinion), it is clear that the FTC have been acting on an incomplete understanding of how hyper scale companies operate, how they can influence a market with their user base etc.