More teams are staying out of the free agent market and rebuilding, because you can't buy enough wins to make a big jump, and this reduces the number of suitors with "cap room" to bid up salaries.
And with analytics, GMs can see how past contracts worked out, and identify the sweet spot both where contracts have positive expected value and where they have a high probability of working in a "win now" strategy.
Analytics have also identified that there's a post-PED drop in performance by older players, which has discouraged long-term deals for players over 30, but also ultra-long contracts (out to age 40) for younger players.