Unexpected results using Anova and TukeyHSD when I halve the groups

I am new to R and hopeless with statistics and its for my PhD.
I am applying TukeyHSD to my simple problem but I get an answer I don't understand.

I have 6 groups of data, and I conduct an Anova test and get p =.45
when I do a TukeyHSD I get a minimum p=.88 on all the groups
If I split the groups into 2, the first group (2L) I get a p =.07
I would have expected the .07 to appear in the TukeyHSD 6 group test
so it's like I need to split into groups (2L and 5L) to get a better p-value but that doesn't make sense so I was hoping someone could clear give me an explanation.


Emboli Artery
1mm (2L) 67
1mm (2L) 43
1mm (2L) 89
2mm (2L) 16
2mm (2L) 9
2mm (2L) 52
3mm (2L) 13
3mm (2L) 6
3mm (2L) 41
1mm (5L) 81
1mm (5L) 9
1mm (5L) 33
2mm (5L) 60
2mm (5L) 1
2mm (5L) 23
3mm (5L) 71
3mm (5L) 0
3mm (5L) 45

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