It is all a bit silly.
Indeed. Because:
1. Easter is named after a pagan goddess of spring and the derivation of the name has nothing whatsoever to do with the death and purported resurrection of Jesus.
2. Cadbury was a Quaker and wouldn't have celebrated Easter as a Christian festival.
3. The world moves on - most people enjoy Easter, but do so as a celebration of Spring and Easter eggs, notion of Easter bunnies etc is simply a reflection of the obviousness in northern Europe of the relevance of the festival to spring, while its reliance to a specific religion belief is for a tiny minority (not dismissing the strength of their convictions, merely pointing out that they are perhaps 5% of the population.
4. Commercial and marketing opportunities are a big deal for commercial organisations (Cadbury's) and third sector organisations (the National Trust).
Nothing to see here, move along please, and (to Semtamu et al) develop a sense of perspective and reality.
Noting too that May waded in on the latest faux 'christian persecution' outrage while bigging up a country that really does persecution on the basis of belief, and most notably non belief, namely Saudi Arabia.